After that I just read some codebases. I find elixir codebases extraordinarily easy to read. The language does a great job of making ‘the good way’ also ‘the easy way’, and the linear nature of functional code is much clearer than the usual indirect dependency injected hell. Papercups is a fairly good starting point I think. I liked the livebook codebases too.
It's not a quick start though: I really dig into how Elixir works and move fairly slowly. I've finished covering the language itself, and I'm about to move into the OTP functionality that's inherited from Erlang.
As others have mentioned on some other threads, learning about OTP, Genserver is really worthwhile. Apart from language, the book teaches a bit about that too. But maybe just enough.
Also, the official docs and guides are fantastic once you have your bearings.