bbbom knows her sh!t, also don't worry about "bulking up" or increaing alittle weight, at your age you are still growing and that will happen. Also, since you are just starting a weight program it sounds, I would recommend sticking to the basics, bench, squat, deadlifts, and powercleans, and then include one or two secondary movements ie flyes, leg curls/extensions, arm curls, trycep extension, dips, pull ups/lat pulls ect.. Getting stronger and in all around better shape will help your riding and in life in general. Good luck and have fun with it.