For more "traditional" or "statistical" modeling (not NN) 100% start with sklearn. It has a plethora of algorithms, and their docs read like a book. You can learn a whole bunch of new methods and techniques from there too. In tandum, you should familiarize yourself with matplotlib, which is the plotting library it uses under the hood (and is by far the most popular plotting library.)

For deep learning, I'd say PyTorch? Tensorflow used to be standard but its fallen out of favor compared to PyTorch. I don't use either so I'm nit sure.