Well, at that, we could respond with tons and tons of bikes..
Be a little more precise..
Where and what type of riding are you going to be doing? Do you have any experience with riding at all? Do you have future plans to race, etc.. things like that?
If your going to be riding in mostly trails and open feilds, and even occasional tracks, the Kawsaki KDX is right up your alley. At that height, you seem pretty tall for a 15 year old, so try and sit on a KDX 200 and see how you fit on that.. if you find it a bit to small, and you want to grow into the bike, then go for the 220..