The guix manual is a good starting point. SystemCrafters has articles on guix and guile but they’re more like blogs and can be outdated. Guix cookbook has some good examples to check out.

Guix source code is also a good way to learn, since most everything is written in self describing lisp you can learn by example. Theres a lot more rough patches in guix than what you’d get with nixos ootb, I’d recommend looking into universal blue first and then augmenting that with guix if you can.