Most people are giving you design advice but I want to give you some career advice, since you're about the age I was when I decided I wanted to make video games, and you say you already have your future planned out.
First off, the absolute best thing you can do for your career is to major in computer science in college. Take any programming classes you can now. I know programming and design are different disciplines. The thing is that the game industry doesn't really hire designers. At least, not in the way you may be thinking. The industry certainly has places for level designers and scenario designers, but they don't hire people who just have good ideas or a good perspective on what makes a good game. You don't have to plan for a career in game programming, but you do need to be code-literate because even as a designer you'll be dealing with scripting languages. Majoring in Compsci is just insurance that you'll get a good job whatever field you're in. All the programmers I know got into games fairly easily after graduating if that's what they wanted to do. It's way easier to switch over to design from programming than it is to just go in as a designer.
There are a couple colleges that offer game design as a major. USC is the only one I can think of that does it undergrad and is widely respected. SMU has a really good, intense graduate program that's known for getting people jobs in AAA studios.
If you're squeamish about programming, then whatever else you decide to do, you have to make games in your free time. If you start now at 15 you'll be way ahead of the curve. Tools like Game Maker, Unity, and Unreal Engine are all great ways to get into real game development. You could also figure out how to mod a game like Skyrim or Fallout and make your own quests and stuff. You basically want to build a portfolio to show off to future employers. Game companies care far more about the games you've worked on than what your degree says.
Games are collaborative endeavors. You want to practice working on a team. There are events happening all the time called "game jams," in which you make small games over small periods of time in small teams. I recommend you participate in these on a regular basis and see if you can rope anybody else into doing it with you. There are numerous Game Jam calendars online, google em.
If you can avoid it, don't work in college. Spend that time making games, or making friends with people who make games. I had to work and between that and my studies I didn't get to work on personal projects, and now I do web development full time (I majored in film). As an addendum, a lot of the people who become successful in indie games come from very privileged backgrounds and didn't have to worry about things like working in college or paying off debt, etc. Don't compare yourself to them.
Lastly: The games industry is volatile, with studios constantly shutting down or taking advantage of their employees. I've had friends move to three different states in one year. They also don't pay you as much as other industries might for the same skills. You're not thinking of any of this now since you're 15, but you should keep it in mind.