i don't think your ready for any type of weights. 14 years old is very young to start lifting, cardio and medicine ball training, by all means, go ahead and do it, but, weights i'd say no. i didn't start lifting weights til i was 16 years old, you don't want to start too soon or else you could get too big in your shoulders, and not be able to pitch much, that is if your a pitcher, if not, you still shouldn't. at least wait another year before you start weights, but, sprints are good, shuffle drills, medicine ball training like you said is good, pitch/hit a lot to get mechanics done correctly, if your a pitcher, long-toss is a great thing to do to build arm strength AND accuracy, try to hit the person playing with in the chest. my suggestion to you is not to start weights quite yet because you could develop too soon and if your a pitcher, you could get too big and not be able to pitch up to your full potential, which i've seen happen to a couple pitchers.