From my own experience I can tell you that Game Maker greatly helps you understand the logic of programming games and even programming in general. Personally, I'd try to do and learn as much from Game Maker as possible before moving on to something more serious, since it is many times easier to make a game in Game Maker than pretty much anything else. And although it has its limits, it'll take you quite a while to start noticing them. Otherwise, it is best to take a uni programming and game design course. Doing both would probably be ideal.