There are already good recommendations here for getting into the "standard practice" of ML.
To really understand what is going on though, the path I am having some early success with (as a long time developer / data pipeline guy, but newly into the standard python / ML practice) is to run through Kochenderfer's "Algorithms for optimization" from 2019 (MIT press), including implementing the exercises, as optimization is the cornerstone of the majority of ML methods. Some of the most fun I've had in a long time.
To really understand what is going on though, the path I am having some early success with (as a long time developer / data pipeline guy, but newly into the standard python / ML practice) is to run through Kochenderfer's "Algorithms for optimization" from 2019 (MIT press), including implementing the exercises, as optimization is the cornerstone of the majority of ML methods. Some of the most fun I've had in a long time.
Freely available here:
https://algorithmsbook.com/optimization/
From there on, I'm less sure, but expect I might experiment with implementing my own deep learning methods just for fun, or similar.