Not to completely disagree with you or anything.... but Seriously?!?
Athletes train with weights, athletes TRAIN THEIR LEGS, I understand that you dont want to be massive, with your body type it would take you a while any ways. But dont compare your body type to an "athlete". Im not trying to give you a hard time, but you post your pic, here is the criticism. Hit the weights, youre under developed every where. My little brother trains only body weight(he is 11). Im going to look through some pictures and post them of him, your body types are very similar. You will not take your body to the next level only lifting body weight. Im all for push ups dips and pull ups. DO THEM WEIGHTED
Goo luck with your goals, but seriously think about hitting the gym, it will take your body from the natural middle school physique to a more competitive level.