Getting started with game programming

I have a pretty firm understanding of Java and now I would like to start making games. What do I do?

I’ve been following a lot of different tutorial series on Youtube, but they don’t seem to help.
Where should I go to get myself a basic understanding of developing games? And what next?
Should I use pure Java or libgdx or something like that?

Please fill me up with EVERYTHING I need to know to go in the right direction, because right now I’m totally lost.