I personally started with Kaggle competitions and lots of googling (duckduckgoing right?), but quite quickly hit the wall of not understanding, I felt like a mindless creature who makes a decision based on couple of guides out there. Watching lectures from Andrew Ng, reading some books helped a lot, but I can't see a reason why one doesn't wanna start with theory. It's no gold and glitter, and no one promised you that, unless you're really want to delegate your work to AutoML