First there is no such thing as gaining muscle fast. It takes time and dedication. Dont consider any supplement out on the market today. Your too young. The only thing you can consider is weight gainers or protein shakes. They will help. The best advice I can give you and I'm sure the other here will agree is to eat like a pig. Thats the best way to gain weight and muscle. A good, clean, healthy diet will add impressive mass to you. Choose a routine where you hit each muscle group 2x/week. Use heavy weight and a rep range of 8-10. 3 exercises per muscle group. But remember there is no magical way to add size. You just have to give it time. The good news is you WILL see results in as little as 3 weeks. Keep it up, good luck and dont be tempted by the junk and promises out there.
the kids too younge to see results in 3 weeks. When i first started out it took way longer than that. Plus, dont bother replying to this guy, he posts the same question a few times every once in a while