There is a lot of information that will benefit you LG in the dieting section. We have kinda touched on this a few times with you because of your interest in trying AS' at such a young age (if I recall, you are 17)
If you are really interested in doing competitive bodybuilding, the very first thing you need to do is research and get a hardcore handle on how to properly diet. Once you learn how your body works, and how to fuel its fire you will have little problem manipluating your size with proper weight training.
There are various workout programs depending upon your goals that you can find in the same diet/training section of this board.
Athletic training is a good thing, but I dont know how many competitive bodybuilders actually do anything more than weight train, and then do hardcore cardio cycles to shed bodyfat for that extremely ripped look for competitions.
At your age, i definitely wouldnt rule out doing athletic excercises because it is good, especially young, to stay healthy overall. So i would say a good mix of workout styles would benefit you until you really really want to start putting on mass for competitions.
