It's a useful reference for trying to talk about various things in Latin that won't come up in any of the usual grammar texts, but it is not a course in Latin itself. It'll come in handy as a supplement later on, though I have mostly used the vocabulary index in the back rather than the lessons broken up by subject. What is really incredibly useful is Traupman's edition of the Bantam New College Latin and English Dictionary. Many of the entries contain concise explanations of the idiomatic uses of certain words. A lot of these may be found in Lewis & Short, but generally not so compactly presented and will tend to be absent from compact forms of Lewis & Short.
Good point, I hadn't thought about English-Latin also. It definitely wouldn't hurt for me to have both, I'm sure I'll find it useful at some point... it looks like the New College one does both? (If I'm looking at the right one, at least?)
Like many, I recommend Lingua Latina per Se Illustrata. You can get a CD to go with this, but these days people have recorded themselves reading it on YouTube. You'll want a grammar book. LLPSI teaches a natural familiarity with the language, but understanding grammar makes that even better. There is a grammar text designed to go with LLPSI, but I have never seen it. There are copies of Wheelock all over the place, though. I also like Lear to Read Latin, because it's what gamers might call a crunchy approach to the language, not afraid to truck in technical explanations. It's Latin for left-brained nerds.
Set a schedule. When got around to seriously studying Latin, I would do at least an hour in the mornings before work studying grammar (back then I was using Adler + the Latinum podcast) and at night I would read a chapter LLPSI. I would read the same chapter each night for a week. Ultimately, in learning to read you want to "read a lot, mostly new stuff" but at this stage I think the repetition helped a lot to recognize patterns.
Do vocabulary cards for anything you're reading. Latin on one side, English on the other, and test yourself. Do paradigm drills. Test yourself. The Natural Method does not eliminate the utility of these study techniques.
Get a copy of Traupman's Latin Dictionary, as your vade mēcum. These days Logeion is my standard Latin dictionary, but Traupman does brief explanations of many idiomatic usages that I often found helped me to understand more than the mere definition did of the passage I was reading. Get used to the practice of looking up words. Seems like a chore for a while, and then it just becomes a trifle.
Traupman. Light weight, fairly comprehensive for its size, identification in a clear, readable format and examples given of idiomatic usages to which you are going to want to become familiar. It's my absolute go-to. It also has the best English-Latin index this side of Smith's Copious and Critical.
Chambers-Murray is regarded as the next best option if you don't want to lug Lewis & Short around.
Ten or twenty years ago, Latinists were wont to say "Cassell's is your friend." It's a big meh for me, but it's useful.
Study your paradigms. Having them memorized makes the thinking easier when you confront them in use. Latin is that class where the textbook gives you the cheat sheet. You are expected to learn that way. Learn your paradigms with the stresses in the right places, and the long vowels enunciated as long. You don't want to have to relearn the words later when you are dealing with verse.
Make vocabulary cards with the English on one side and the full Latin identification on the other. Use the simplified definitions given in the book; do not try to encompass at this point the subtly different senses of the word you can find in a separate Latin dictionary. The subtly different uses of the word can be added to your understanding later. But learn the whole identification of verbs even before they teach you what the last two principle parts are for. Practice both English-to-Latin and Latin-to-English.
Get yourself a copy Bantam's New College Latin and English Dictionary and carry it wherever you go. Spend time looking at definitions you run into. You should also consult the English-to-Latin section anytime you wonder about the Latin equivalent is to some word or phrase in English, though these days you should also have a link to these searchable dictionaries on your phone:
https://latinitium.com/latin-dictionaries/ - Great for English-to-Latin, searches multiple sources. The English-to-Latin section in Traupman is basically a boiling down of Smith's Copious and Critical. Doderlein's Synonyms will help you learn a lot of nuances in word usage.
https://logeion.uchicago.edu/lexidium - Logeion searches multiple Latin dictionaries, including Lewis & Short, but also more obscure ones and it often brings up entries from DuCange, a Latin dictionary written in Latin.
http://www.archives.nd.edu/words.html - Helps you find the lexical form of an inflected word, and is also useful for doing English-to-Latin translation.