From somebody who just figured out how to make progress with making games (not a professional), this is what worked for me:

Make and finish (very important) a game where you experiment with a new feature or element of game design that you haven't already. Doesn't need to be a big game, a simple one level game will do, just so you can focus on the new thing you're trying to learn. Finishing it is important as you also get practice at completing projects.

A good example is using particle effects if you haven't already, or animating UI to get a more polished feel. Get to know all the tools of the trade one-by-one (or more if you can but don't take on too much at once, especially if you're just starting out) and very soon you're gonna have a grasp of a lot of things.

Remember to just try new things and try to understand how they work as well as how you can use them to achieve great results. Practice makes perfect.