I have similar interests for the future - when I can work or study again (sickness... legit, unlike most)

I actually came here to make a post like this but saw this thread and figured it'd be more practical to simply expand on it.

I only have experience with fedora core 6 and linux redhat 7-9, needless to say it doesn't go far.

I can't afford the courses/books, so where should I begin in my journey to learn what is necessary?

Thanks for advice.