I done the P90X program and I can tell you it worked great! I used it as I just got over an injury and could not go to the gym, and p90 was great! as the the nutrition I followed my own and just ate healthy and lean, used creatine and protein and I was happy with how I looked after.
If you have a gym member ship and are wanting to gain some muscle first I would suggest a H.I.T style program for 4 weeks or so, up your calories and protein and you'll be happy with what you gain, especially at your age. then when you have done that and want to lean out some try the p90.
good luck bro.