I learned a lot about pandas (a library built mostly on top of numpy) by going to stackoverflow and trying to answer questions with the tag. Hopefully the questions have a minimal reproducible example and are isolated to one specific question
That's like saying "what's the best ingredients to learn cooking with?", firstly it all depends on what your want to eat, secondly it doesn't really matter what the ingredients are to learn cooking skills.
Standard library of course. And collections module too, among the others that come by default. What you need is assignments to solve. Like project euler or hacker rank.
Make a plan of what you want to build. Start with the standard library. Google things you don't know how to do, those libraries will show themselves to you.
Thanks but Im just going to go ahead and do my own thing. Everyone's very insistent about doing things a certain way in this thread and honestly its unsolicited advice. Not everything is an XY problem :). I'm just going to install my different, unconnected libraries and tinker in peace