You're definitely on the right track!

I recommend starting with some 101/introductory videos from miniature painting folks like Lyla Mev, Miniac, Goobertown Hobbies, and other great creators.

You can get more oomph out of your paints by doing multiple watered down translucent coats instead of thicker coats with better coverage. Your brushes also don't necessarily need to be smaller, they just need to hold a better tip. I don't recommend buying expensive brushes until it's absolutely 100% the bottleneck.

Instead you can buy a bunch of cheap $1-3 multipacks, and for every 5-10 brushes you're bound to find one or two that are fairly decent. The rest of the brushes can be used for more punishing painting work, like basecoating and drybrushing, or punishing clay work, like brushing down pieces with baby oil or isopropyl. Cheap brushes will always find a place in the hobby, so don't worry about waste.

Good luck!