reminds me of when i started what, 3 years ago?
being about the same age as you (15), from my experience, get the kit so that after you bul it you understand it. I wnet rtr with my first car, and didnt know squat about how to fix it, and the fact that rtr's manuals dont come with detailed manuals, it makes it DOUBLE HARD to learn your car on the bench.
but hey, keep racing and you WILL get better, it took me about 2 years to get really competitive (like regionl competitive), but if you keep working on it, the potential for future local fast guy will always be there. I was a competitive driver 1.5 years ago, but a car can really hold you back. I had upgraded to an academy str-4 for my first indoor season, but once I bought a cyclone the end of the following summer, it was amazing how much having a decent car improved my driving and competitiveness. If you get a high end car in the short run, it is more expensive, but in the long run its cheaper cus you can use that chassis for 4 years and still be competitive, wereas with other cars the chassis design is inherently limited, and you might by a new car every 2 years, which is much more expensive in the long run. if you want to talk just PM me man.

Mike