I would start by taking a project I like and setup a basic devshell for it, using some LLM and the nixos learn section as a guidance and as a learning tool to explain steps and dive deeper in certain topics.

E.g. nix-bitcoin is a highly configurable nix project that you can use to define and run an onchain/LN node, joinmarket and other bitcoin related software.

Nixvim is another one if you like neovim.

Or just grab a project that has a devshell already defined and try to make it work.

[Notedeck](https://github.com/damus-io/notedeck) is an example that is nostr-related and has a nix shell defined that you can play with.