I want to get good and defending myself

Go to class.

You could do MMA. Then again one martial art is enough to be able to defend yourself. That didn't stop me though. I would say try Muay Thai kickboxing it's a pretty good class. If you want something more challenging try Brazilian jiu-jitsu. If you want you can try both. Just don't start fights with random people or for simple reasons. I only fight when it's necessary like when someone is getting picked on.

Do Stretches, Stretching out every part of your body, Then, Practice Some Kicks and Punches and Blocks or Parrys and Dodges And Movement, Then Do some Sit ups and push ups and Squats, and then practice fighting Again in your own way, Make you exercise your whole body with Martial Arts and normal Exercises.

Watch MMA based YouTube videos showing training. I recommend watching mark Munoz,lyoto machida, Jason mayhem miller work outs

Kajukenbo or sanctioned Kajukenbo other arts like Boxing Grappling and Kickboxing.

We do things like this and more:

http://www.akban.org/fitness/