Any workout tips for me :P?

Check out Reddit.com/r/Fitness - Those guys have led me to a healthier life. I've lost 20 pounds, and am lifting twice what I was when i started. They have a ton of good advice and programs to help you achieve your goals.

Look up Cross Fit.

Drink water, lots.

I'm not sure if this is true, but i heard that after a day of working out, you should let your body rest for a day.

Is it even healthy to workout at 14? I mean, the guy can do sports alright, but intense workouts? Doesn't that potentially mess with the normal growth?

That aside, you need basic leg training. Like others have said, plenty of sources on the internet for precises trainings. And you can do your own too, since you just want more strength (though probably not the mass).