As a 16 year old, you have a good base to work with. I would recommend three things immediately:
1. Lose the Knee Savers. This should allow you to get lower in your stance. Also along that line...get more flexible in your hip flexors. Take a yoga class. You have a pretty good sized frame and you will need to present a low target at times. Flexibility is very important.
2. Find a long toss or arm strengthening/stabilizing program. We use Jamie Evans' Velo-City (http://www.baseballvelo.com/).
3. Footwork - your feet need to be faster. Jump rope or agility training may help here.