I started in Karate when I was 8 and it really helped me with the fundamentals. You know, turning the hips on kicks and throwing punches correctly. It also gave me a system in which to gauge my progress. But I have found Muay Thai Kickboxing to be much more helpful. Muay Thai is great for MMA, mixed with some defensive wrestling and a good jiu-jitsu game from your back. Because in Muay Thai, if you are throwing kicks and knees, you will most likely be taken down at one point or another. Getting back up quickly or hitting a sub is a great way to make use of that weakness.