Well, you are too young to take anything hormonal. Stick with Creatine and a quality weightgainer like Ergopharm's Mass Meal, Cytosport's Cytogainer or Milk Muscle/Milk Muscle Collegiate. Try to find 3 days to lift a week. You could try:
Monday : Bk/Ch/Sh
Wednesday: Qds/Hms/Calves
Friday or Saturday: Bis/Tris/Forearms/Abs
Stick with compound exercises and maybe a few sport specific exercises that may benefit with baseball. It only takes about 60-75 minutes a day 3x a week to see good results. Keep track of your calories and if you aren't gaining muscle/strength then bump them up until you do.