A lot less trolls there...
Look into more workouts just using your own body weight for that age, push ups (wide, narrow, military, triangle, incline for added resistance) sit-ups, etc. You don't need to go to the gym to stay fit you just need to do physical exercise. But don't start experimenting with supplements yet, at that age since your body isn't done growing yet. Just try and eat healthy, but if your really interested check out those forums, a lot of good info on there!