I would say the next step after remaking simple games is to make new simple games. Or rather, make some rapid prototypes. When I was first starting to learn Game Maker, and after I did the basic tutorials, I set out to make one game prototype a week, which I did for four weeks. The trick to this is to come up with one clever/unique gameplay mechanic and create just enough of a game to test it out.
Once I was done with this, I felt quite comfortable with Game Maker, and could move smoothly through it. I then made a full game out of one of my prototypes. By full game, I mean graphics, sound, and a fair deal (in the case of this game, 5) of levels. I completed this game in about a month.
Try to keep your first few projects at around this time-frame. Of course, as you get more and more comfortable with the tools, you'll be able to make larger games within that time-frame.
Once you have some experience going through the whole design process from concept to finishing and release, then you can start to tackle longer term projects. I personally like to have a few projects going on at once, of varying sizes, so that even while I'm working on a larger project, I have some smaller projects which I actually get to release.