I've put together a catalog summary of some of my X16 related projects here:
https://voidstar.blog/best-of-voidstar-x16-content/
Many are intended as short starter examples. If you're a "learn by example" type person, there may be some useful reference code. But not any initial step-by-step guide, such as one thing missing might be a tutorial on how you can edit code by just driving the cursor around on the screen. That's a pro and a con, since you can press ENTER on a line and inadvertently have other content on that line get saved into your program. Or things like "quote mode" (and getting frustrated on why you can't cursor away from line since you're in quote mode)