Gesture Magicians: Gesture magicians don't actually require any physical components to work their spells, and as such, they have to have some inherent ability. You are either born with this ability or you're not. Sometimes it's strong, and sometimes it's weak. The stronger you are, the more complicated a spell you can do; for example, it's the difference between being able to make one magical knife cut versus making a very fine dice.
All spells done by gesture magicians are made up of hand gestures and movements, done in a precise way. It's as much art as science and science as art. Many magicians have books of spells written in shorthand, that explain the basics of the gestures they have to do.
Gesture magicians also, like many magic users, have a tendency to make technology act up. The stronger their magic, the more haywire tech gets around them. Strong spells can fry cell phones, TVs, or even electric lights.