1. You could Google the authors/books/courses.
2. I did a CS degree but I worked almost full time as a freelancer learning technology while I was at University (this helped me pay my University fee and also make extra money for everything I wanted to try like different ventures).
3. For marketing. The basic ideas came from doing my own ventures. When you really need to get the word out, you start using social media, link building, backlinking, SEO, SEM, Ads etc. There are really good Udemy courses for that (try the ones that are free). I read the book called 'Traction' for exploring marketing channels. Its great. Most of the other things come from daily feed coming from different sources. I like gary vaynerchuk's stuff on it these days.
4. I combined marketing by giving business ideas and opportunities for expansion to each employer I worked for. Things like sharing links to good content, doing analysis of competitors and helping young marketing guys (in startups).
5. Read a lot. Don't try to be someone else. Adopt the things you like in someone and keep moving!