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One thing I would recommend is the Google Primer App. Although it's by Google, it's not about SEO but marketing and PR in general. But it does include sections on how to approach bloggers and the like to get PR which can equal links so is relevant to this question. But there's also good stuff for noobs in other areas of marketing too.
I highly recommend it as a quick low bullshit intro to marketing with practical examples.
https://itunes.apple.com/gb/app/primer-marketing-lessons-for/id918628107?mt=8
https://play.google.com/store/apps/details?id=com.google.android.apps.primer&hl=en
These are UK links so you might need to search your local App store for "Primer - marketing lessons for startups"
This one is pretty cool: https://play.google.com/store/apps/details?id=com.google.android.apps.primer. It kind of pushes what material can do.
Google Primer for bite-sized marketing lessons.
Grasshopper to learn JavaScript.
Primer- Bite-sized marketing lessons with offline functionality.
Science Journal- Use the sensors in your smartphone to conduct and record scientific experiments.
Snapseed- An excellent photo editor with RAW support.
PhotoScan- Scan and save high-quality images of your old photo prints.
Drive- The best cloud storage solution.
Gboard- A multilingual keyboard that successfully replaced SwiftKey for me.
Files Go Beta- A storage manager that also lets you share files offline (like SHAREit).
Search (Test App)- A lightweight alternative to the Google app.
Maps- An unmatched navigation experience with live traffic data, public transport schedules, and offline maps.
Primer- Bite-sized marketing lessons, offline.
Science Journal - Use the sensors in your phone to conduct experiments and record data.
Encode - A beautiful app to learn the basics of JavaScript with bite-sized lessons.
Collegiate - Take free courses from renowned colleges and institutions.
SoloLearn - Learn coding in various languages interactively with the support of a growing community.
Google Primer is an excellent way to learn business and marketing skills with bite-sized lessons.
For digital marketing, google came out with primer which is kinda basic but its all very well presented.
Another ideas is to find freelancer work on a website dedicated to that. Whether you have a talent for designing the look of a brochure or website for a client or have knowledge of computer coding, that may be able to get you a little money. There is a list of about 20 such sites at https://webflow.com/blog/freelance-websites.
You can try to use canva.com to help design pieces or work or projects for clients. Try using openoffice.org or libreoffice.org create documents, slide presentations, or posters. You can learn basic programming and coding through https://www.freecodecamp.org/ and khanacademy.org with other sites listed at https://skillcrush.com/blog/64-online-resources-to-learn-to-code-for-free/, learn digital marketing and business skills via https://play.google.com/store/apps/details?id=com.google.android.apps.primer, or you can look at online audio transcription work and learn about reviews of companies that do this kind of work at https://www.youtube.com/watch?v=CeiOM2og4_A.
Google has a phone app called Cricket that helps you learn to code at https://play.google.com/store/apps/details?id=com.area120.grasshopper.
Google Primer has some crazy animations:
Google Primer- bite-sized digital marketing lessons while you take a dump.
I will list some apps for you. Check them out for ideas (and source):
1) https://play.google.com/store/apps/details?id=com.google.android.apps.primer&hl=en
2) https://play.google.com/store/apps/details?id=com.google.samples.apps.iosched&hl=en
3) https://play.google.com/store/apps/details?id=com.rey.material.demo
4) https://play.google.com/store/apps/details?id=com.sagar.materialdesigndemo
The latest design trend is called "Flat 2.0" which is an even simpler version of "Flat" which what Material Design is based on. You can Google these words to learn more.