Hi, I'm 14 weight are very helpful at the age of 13 and less pylos. You also need to put on about 50lbs of weight. So start doing stronglifts.com 5X5 or email me at straylight516 at gmail dot com and I'll show you how to obtian the vertical jump bible. The fastest way to increase your vertical jump is to increase you strength so weight training will be key. Also, I doubt you are very strong because of you weight so don't focus to much on plyometrics. I feel for you being an overly skinny kid as I am myself. Although, I put on 20lbs to get and grew 4 inches to be 5'7" and 130lbs. So, start weight training stronglifts 5X5 beginner or Kelly bagget's novice program. Some light plyometrics could be integrated and start eating more.

Any more questions?