One of the best pieces of advice about jiu-jitsu I ever got was at about your age, when I thought I wanted to train jiu-jitsu and fight full time. (I changed career paths for a number of reasons; its a good path, though.)
The advice was this: When you're young, learn as much as you can and work as hard as you can. That means learning from the coaches that you have, from guys who are traveling through who stop by to do seminars, from folks in areas that you visit. Learn from all of those people.
Drop in on gyms and train with those guys. I've dropped in on 10th Planet places where my friends train; I've dropped in on one of Jake Shields' gyms that is pretty close. You may not be able to do it until your 18 without having your parents sign a waiver, but its still an important thing to be in the habit of doing. That's a great way to keep your mind and game open to cool stuff and to make sure that you are constantly evolving and constantly finding new things to think about and be aware of. It also keeps you from getting surprised with stuff you haven't seen before, which can be really dangerous in a fight.
The other thing is to try to be creative yourself. Try to come up with moves and approaches to attacks and variations on moves that you've seen folks use. Ask your coach how these things work and how he'd respond and whether he thinks it'll work. Creativity is one of those things that is seriously underrated in MMA, but the guys who go far are often the guys who are constantly inventing; Miletich, Shamrock, Couture, Anderson Silva, etc. etc. etc.
The only other advice is just to keep at it. Keep pushing yourself. The best thing is to stay thirsty for more in the gym. Be a glutton for punishment and try to improve yourself. That's how the guys who are really freaks of nature in MMA get good.
Sig by Toxic
Barnett - Toquinho -Werdum - "Nurmie"
Z. Gurgel - Morango - Rocha - Tiequan