To be honest I am still using Game Maker Studio 1.4. I am not a fan of the interface in 2. I'll switch one of these days.
I started programming in Game Maker probably 5 years ago. I did some games in java a few years before that with Slick2D. I learned at first with a few videos on YouTube creating some small games. The first game I made was a Flappy bird clone with lots of different birds and costumes. Anything I couldn't figure out I Googled.
Googling is %90 of programming. The other %10 is coffee. :)