Well start by doing the two things you mentioned your not doing! Damn bro, nutrition is essential. I mean even if you were using gear you wouldn't make huge gains if you don't eat right.
Also at your age (nothing against your age, we were all there once), make sure your training regimine is a good one. Pay attention to over training, you young bucks can get a little too zealous when it comes to training. Being motivated is great, but your body needs it's rest time.
I'm sure you've already heard it, but stay away from the gear. Your growth plates need to close on their own, gear will fuse them early and there goes any good height or bone development. You can see if your bodies growth plates have already fused by having an x-ray done of any major joint (knee, hip etc.).
Just some tips.
Asta