Im 15 and i want to train, lean how to fight and be combat effective. where do i start?

Ok so after i enlist i want to be the best(marine) of the best(green beret) of the best(delta force). hah but humor aside i want to be the best i can NOW and start training, i am currently taking cajun karate and thats great but i feel as if that is not enough. i dont know what to do and i need guidance and someone to steer me in the right direction. and right now i have this burning desire to fight and i dont know why