I'm doing chinese. Where to start depends on where you are already. r/MIA_Chinese is worth checking out. Since you've already been studying chinese, you may already have a lot of good resources and might know of some of these (and might have many better ones). Idk what will be useful for you, so I just listed some resources I could think of.
Some potential resources, anki decks:
Grammar guides:
Hanzi Books:
Apps/Extensions:
Some possible immersion starting places:
EDIT: Also, wood_da_beast posted an MIA Chinese Guide a while back: https://www.reddit.com/r/MassImmersionApproach/comments/fofane/mia_chinese_quickstarter_guide/ . It links to an excel spreadsheet that I think is very helpful for getting an overview of what you might want to do and what stage you're at. It also suggests some good resources for each stage and activity. https://docs.google.com/spreadsheets/d/1N_LV9aQDvrg1TT5QYG--Ubkv-YjRUjPs3uodk8a6b04/edit#gid=0
Yes, radicals are only the character component under which the character is sorted in dictionaries. The characters are separated under various headings (i.e. radicals) and then sorted under that heading according to the number of strokes in the non-radical parts of the character (i.e. the total number of strokes in the character minus the number of strokes in the radical).
However, all characters are composed of one or more components. Each of these components may then also be composed of one or more components, in a nesting hierarchical nature. For example, 旦 = 日 + 一, while 查 = 木 + 旦 (and not 木 + 日 + 一). That is, 旦 is one of the components of 查, with 旦 being composed of its own components. To further the example, the radical for 查 is 木 and would be listed in a dictionary under 木+5 (where the +5 refers to the number of strokes beyond 木).
Such a hierarchical structure for the characters actually makes it much easier to learn them, as you can learn them in a Lego-block-like fashion, building up from the smallest characters. See this website for such an approach: https://www.hackingchinese.com/creating-a-powerful-toolkit-character-components/
This book combines such an approach with a very useful mnemonic technique:
"Tuttle Learning Chinese Characters: (HSK Levels 1 -3) A Revolutionary New Way to Learn and Remember the 800 Most Basic Chinese Characters" by Alison Matthews and Laurence Matthews (https://www.amazon.com/Tuttle-Learning-Chinese-Characters-Revolutionary-ebook-dp-B00KV1SK1E/dp/B00KV1SK1E/)
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For more information about what to learn concerning radicals themselves, see this site: https://www.hackingchinese.com/learn-pronunciation-of-radicals/
These are not the best, but useful. Tuttle Learning Chinese Characters: (HSK Levels 1 -3) A Revolutionary New Way to Learn and Remember the 800 Most Basic Chinese Characters covers 800 common characters, has vocabulary overlap with HSK, and uses a mnemonics system to remember the hanzi where the book does all the work of coming up with the mnemonics stories for you (unlike Heisig's books). The mnemonics cover meaning, and pronunciation including tone. I found this book really useful for learning a lot of hanzi quickly and early, so I could start watching shows after a handful of months and reading graded readers. After this book, I found learning new hanzi from words I studied easier just because I had some foundation and a good idea of how to recognize radicals in new hanzi, and how to come up with a story to remember new hanzi. Mileage may vary with this book, and there's some other really good hanzi-learning books. But I found this one made the biggest difference in how quickly I was learning hanzi and then words afterward. The book comes in simplified and traditional versions.
Other good hanzi learning books: Chinese Characters: Learn & Remember 2,178 Characters and Their Meanings by Alan Hoenig. It only covers hanzi meanings, but if you like the mnemonics style of learning characters, it has stories for every hanzi (unlike Heisig's books) and covers ~2,000 hanzi (so more than the book mentioned above). This comes in simplified and traditional characters. Reading and Writing Chinese: Third Edition, HSK All Levels (2,633 Chinese Characters and 5,000+ Compounds). This is a good reference book for hanzi, there is a simplified and traditional version.
For lessons, I am not sure what the best textbooks might be. I personally liked this free site and just went through it when I started learning: http://www.chinese-grammar.com/ . Then after that, I used Ben Whatey's 2000 common chinese words memrise deck, and Chinese Spoonfed Anki decks. After that all my learning was done from reading/watching/chatting. I think the "Immersive Chinese" app is also fairly good, I've been going through it to review, its laid out very straightforward and covers a good amount.
Integrated Chinese is a popular textbook series, the University near me uses it, and I think that would also be a solid resource to use. If you have a library, especially a University Library you belong to, I would recommend going to the library site and searching 'chinese textbooks' as usually University Libraries have ebooks of quite good textbooks. I think which textbook will be best for you depends on the approach of the writer. I'd just say try to find a book that covers a significant amount of vocabulary, covers tone sandhi and other tone features (as well as looking tones up on youtube or online for some audio examples and further clarification), and introduces hanzi early on so you learn them as you learn the words. I've seen some very poor chinese textbooks that cover less than 200 words after the entire book is completed, and less than 100 hanzi. They were a waste of money for me. Especially when there's a lot of great free online resources that cover much more.
These are some suggestions, you may want to not use them and that's okay. Personally, I think it's okay to transition to using hanzi With pinyin (like pinyin above) and still rely on the pinyin for a while, just because constantly seeing the hanzi at the same time may help the pronunciation eventually stick for you. When you start moving to hanzi only, I recommend listening to audio as you read, so you can hear the pronunciation of hanzi and again use that to help you use hanzi pronunciations. There's some graded readers with audio, reading graded readers (or anything) on something like Pleco app you could use the speaker-phone icon to hear everything read aloud, and there's some graded readers with pinyin above and a cover for the pinyin so you could practice reading with and without pinyin aid. I don't think its bad to keep using pinyin while you need it, I think I used it until I had studied like 2000 words (so maybe HSK 4ish). I do think that shifting to no longer relying on pinyin is not as hard as it may seem, the mind adjusts. Your mind knows ni3 and 你 are both "you" in chinese, its just not recalling the 'ni3' pronunciation super fast when you see 你 yet. (Not a great example but its this kind of idea). So if you only use the hanzi, your brain has the pronunciation info for that word it just has to practice remembering it when it sees the hanzi with that word meaning.
I also would really recommend checking out this book, if you have a local library or belong to a college so you can use their library then this book is usually free as an ebook check-out. For sale its usually $15 or less. Tuttle Learning Chinese Characters: (HSK Levels 1 -3) A Revolutionary New Way to Learn and Remember the 800 Most Basic Chinese Characters. This book specifically has mnemonics for meaning AND pronunciation including tone. I used this book when I started, and the mnemonics for pronunciation helped me so much. And after going through enough hanzi in the book, it gets easy to make your own pronunciation+meaning mnemonics for hanzi. The book's inclusion of pronunciation in the mnemonics made remembering tones easier for me, and overall just remembering hanzi way easier for me than it had ever been when I learned japanese (where I used meaning only mnemonics). This book may or may not click with you, for me it made linking sound to the hanzi in my mind much easier.
Check out Chinese Spoonfed anki deck and Chinese Spoonfed audio files. The audio files with chinese and English sentences may be useful to you, and also Glossika Chinese sentences audio may be useful. Glossika is very suited to learning listening/speaking primarily. The Chinese Spoonfed anki deck has audio and characters/pinyin, so you could just mainly focus on pinyin/audio and still see the characters frequently to just get some exposure. So later when typing you'll know what hanzi looks familiar for what you're trying to type, or if you end up wanting to learn hanzi later.
If you truly want to learn chinese only for speaking, audio only resources may be useful to you. There's not a lot of text resources for pinyin that go very far into actual proficiency speaking, and if you plan to use text resources then you'll want to pick up some hanzi familiarity for stuff beyond the very beginner materials. Hanzi aren't as hard as they look, but they do feel a bit harder if you wait to learn them until later. For learning vocabulary in some ways hanzi are way easier than pinyin, because hanzi have radicals that often tell you the pronunciation and give you a hint at meaning. Whereas if you see/hear gu3jia4 you don't know if it's 股价share price or 骨架skeleton (today Google mistranslated it as share price since it's the more common word with that pinyin to Google lol). If you see pinyin/hear shi4 you don't know if it's 室, 世, 士, 是,etc. In listening you eventually have to guess and learn to tell when it's which word, so for listening you'd have the ambiguity anyway. But as far as learning from reading material goes, ultimately stuff with only pinyin will get confusing as these situations come up. Where if you start learning hanzi, learning with reading material ultimately adds up and teaches both pronunciation and the look of hanzi so later when you see new words you see familiar parts helping you guess new word meanings and pronunciations. Down the road, if you do feel like learning hanzi, you may find it makes some learning materials easier to use. I personally found this Tuttle book made hanzi quite doable to start learning without too much work.
Tuttle Learning Chinese Characters is a classic book that I cannot recommend enough. It has a totally different (and fun) approach, hacking our brains' ability to remember images and stories much faster than rote memorization. It has been around for a long time, so you can probably find a used copy cheap.
This is it from the publisher: https://www.tuttlepublishing.com/language-books/chinese/character-books/tuttle-learning-chinese-characters
and with the original cover: https://www.amazon.com/Tuttle-Learning-Chinese-Characters-Revolutionary-ebook/dp/B00KV1SK1E
Seriously, check it out.
Tones: 4 Tones video, Best Way to Get Better at Tones video, and the https://www.dong-chinese.com/learn/sounds/pinyin pronunciation guide (go through each lesson in order and listen to everything).
Grammar: I honestly recommend just reading through an entire grammar guide (or at least the basics portion of one). Read a grammar guide summary if needed, sentence structure explanation articles if needed. Find a pinyin-including grammar guide if needed, and just read it all in pinyin. If you want to understand the grammatical rule first, reading a grammar guide will help with that. This is what I did months 2-3 of learning chinese and honestly even knowing literally nearly no hanzi at all it was still completely doable. I just read through all of the lessons on a free grammar guide website http://www.chinese-grammar.com/ . There's also AllSetLearning's Chinese Grammar Wiki site which is great if you want to look up a specific point more in depth. You could also read it through, just keep in mind it is long. If you wanted, you could pick any course/book/method in the world you liked and just reference the Chinese Grammar Wiki as you cover each related topic. Again, there are pinyin only resources and pinyin-including resources for courses/books if you are not learning hanzi fast.
For hanzi: try to start learning them as soon as you're ready. Mnemonics help, there's tons of anki/memrise flashcard decks out there if you search "hanzi mnemonics anki" or "hanzi mnemonics memrise" on google. Skritter is also an app for hanzi learning I've heard is good. There's also tons of free user made courses for chinese on anki and memrise if you search.
I would recommend reading the following 3 articles for steps to break down hanzi into much easier to understand pieces. Hanzi are only made up of a little over 200 radicals, radicals are easy to recognize, and once you start noticing them it is easy to break hanzi down into them visually and remember them. Radicals also often hint at or provide pronunciation, which is nice. Articles: How to Read Chinese Characters: A Beginner's Guide, Learn to Read Chinese with Ease, The 100 Most Common Radicals. And this is a list of the radicals with audio: Chinese Character Radicals.
I recommend the book Tuttle Learning Chinese Characters: (HSK Levels 1 -3) A Revolutionary New Way to Learn and Remember the 800 Most Basic Chinese Characters. If you have never tried to learn hanzi with mnemonics or struggle to, this book is nice. It goes through 800 common ones (up to HSK 3), and has a premade story to help you remember the meanings, tone, and pronunciation of all of them. When I studied from it I literally just tried to read a few pages a day. I only got through about 500 hanzi in the book, but by then I was finding it much easier to recognize at least half of the hanzi in new words (I was doing 2000 most common word flashcards on memrise). And that made it easier to learn the words. Then once I had learned those words I knew enough hanzi roughly that I did not have many issues picking up more after that over time through reading. There are also many other hanzi learning books that may be of use to you if another method clicks better with you.
Everyone's already given solid advice. I wanted to add that if you want some learning material suggestions to start with, I used the following books for my first hanzi/vocabulary and I thought they were helpful. As a beginner, specifically the book Tuttle Learning Chinese Characters: https://www.amazon.com/Tuttle-Learning-Chinese-Characters-Revolutionary-ebook/dp/B00KV1SK1E . The book teaches 800 hanzi including main meanings and pinyin, a decent amount of frequent words and early HSK words, and its specific mnemonic story structure I found worked well for me. Also unlike some of the books listed below, this had mnemonics for every single hanzi. Took a month or two to pick up 400 hanzi from the book, then I went to just learning vocabulary generally. I found that book very useful.
After that I used anki decks, textbooks, words looked up when reading etc. Of the anki decks, one was 3018 Simplified Chinese Hanzi Mnemonic deck: https://ankiweb.net/shared/info/1219175376 . There's also a traditional hanzi version of the deck. I added pinyin so I could study that too, and learned about 500 more hanzi with that after I already had somewhere over 1000 well grasped from previous learning materials or the words I'd learned while reading. After that, going back to picking up hanzi while learning words went pretty smoothly. That is what I do now.
There are also the books: Reading and Writing Chinese: Third Edition, HSK All Levels - I have this book, and while its more like a reference book, it has a lot of useful information. It has example vocabulary, stroke order, main meanings. The only thing I didn't like is about halfway through it shows the rest of the hanzi with much less details about them. Alan Hoenig's Chinese Characters: Learn & Remember 2,178 Characters and Their Meanings - I like this book a lot, as it includes mnemonics and pinyin for each hanzi, and worked well as a secondary resource to help me remember hanzi when I learned them in words if some were not sticking in my memory. Heisig's Chinese Characters - I have not used this book but some people have and found it helpful, I've glanced at this book and its also more of a secondary resource to help you recognize/remember hanzi, but I found the other books mentioned better for including pinyin too/vocabulary too/stroke order/mnemonics or something to help with memory for more hanzi.
Hacking Chinese has a free crash course on how to learn Mandarin and many, many articles with advice about learning Mandarin: https://www.hackingchinese.com/
Also, for character learning, I strongly recommend this book: "Tuttle Learning Chinese Characters: (HSK Levels 1 -3) A Revolutionary New Way to Learn and Remember the 800 Most Basic Chinese Characters" by Alison Matthews and Laurence Matthews (https://www.amazon.com/Tuttle-Learning-Chinese-Characters-Revolutionary-ebook-dp-B00KV1SK1E/dp/B00KV1SK1E/)
Not only is the approach they use very helpful, it also helps you learn how characters work, which is vitally important and will make your life much easier. While I admit the HSK levels in that book are referring to an older standard, you will need to learn the characters in that book eventually anyway as they are pretty common.
I strongly recommend using the technique described in the book "Tuttle Learning Chinese Characters: (HSK Levels 1 -3) A Revolutionary New Way to Learn and Remember the 800 Most Basic Chinese Characters" by Alison Matthews and Laurence Matthews (https://www.amazon.com/Tuttle-Learning-Chinese-Characters-Revolutionary-ebook-dp-B00KV1SK1E/dp/B00KV1SK1E/). The technique is effectively a mnemonic technique with principles similar to those of memory palaces. The technique not only helps you remember meaning, but also pronunciation (including tone). Also, the technique works by using components in the way they are used in characters. That is, you learn the simplest characters first, which have no components other than themselves (such as 木 (tree),一 (one),日(sun)). Then you learn characters that have those simplest characters as components, such as 旦 ( = 日 + 一). Then, you learn characters composed of characters, such as 查 (= 木 + 旦) and continue to build up from there. Note that this is different from taking 查 to be composed of 木 + 日 + 一. Characters work via the former method (查 = 木 + 旦), not the latter.
To break down the characters into components, I find wiktionary (https://en.wiktionary.org/wiki/%E6%9F%A5) to be incredibly useful. Usually, I can just copy and paste the character into wiktionary's search bar and the resultant page will give me the character components listed as "composition" in the "Han character" section.
Beyond this, a Spaced Repetition system (such as Anki) is immensely valuable for review (https://www.hackingchinese.com/an-introduction-to-spaced-repetition-software/).
Also, because this confusion abounds: note that radicals are not the same as components. Specifically, all radicals are components, but not all components are radicals. All characters are composed of one or more components, while only one of these components is the radical of that character. For example, 好 has the components 女 and 子, with the radical being 女. For more, take a look at https://www.hackingchinese.com/learn-pronunciation-of-radicals/ and https://www.hackingchinese.com/creating-a-powerful-toolkit-character-components/
Well, there is this list of the most common radicals, which would also help you. http://www.yellowbridge.com/chinese/radicals.php
And if you are learning simplified hanzi, you can consider using this book: https://www.amazon.com.br/Tuttle-Learning-Chinese-Characters-Revolutionary-ebook/dp/B00KV1SK1E/ref=sr_1_1?ie=UTF8&qid=1478521960&sr=8-1&keywords=chinese+characters+tuttle
It always introduces a non-compound character before using it in a compound character