If you can train a throw/takedown-heavy martial art, like wrestling or Judo, that would help. He who controls the takedowns controls the fight, either by out-grappling the other guy on the feet to keep the fight standing (Aldo, Liddell) or by taking a superior striker to the ground (Couture, Sonnen). Guys who are good on the feet and the ground tend to lose to guys who are good at that in-between zone of clinchwork and takedowns (Condit, Nick Diaz, Gonzaga, Mir).
Well if you focus on those two you will be fine but I would switch out bjj for judo and then return to bjj later.
A good Judo club will work standing and ground techniques 50/50 and judo is more fast paced so it will be good at making you explosive. Judo will also work well with your clinch game in Muay Thai. Bjj is great, I took it and love it but the slow pace and lack of standing techniques leaves something to be desired. Bjj is something I would add later for more ground techniques otherwise judo is more well rounded.
Just find a good school and train. Preferably a mma school since your goal is mma. Most people might recommend boxing. Every mma school don't teach the same combat sports.
If you can find a real instructor, learn the Old World Japanese system of Jujutsu. It is the Samurai hand to hand system designed for open combat. It teaches disabling and critical striking, as well as clinch, throws, and grappling. It is a more intensive system than the typical Jujitsu, or Judo, program. Wrestling and Judo have their individual benefits but your trainers would have to help you incorporate them into your fighting system. Jujutsu is more complete in that aspect as it contains more variation to accommodate adaptability.
Im 15 and train in Muay Thai and BJJ. Im going to start mma when im 18. Should i train something else before i go to mma? I have 3 years to train something if so..
