Welcome to the Chalkbucket. Just a reminder that we use full sentences and we do not use MSN speak here at all.
For hair and music use the search bar at the top and it will bring up our most popular threads on the subjects of hair and music. Your coach should really help with the music though. What level will you compete?
I stumbled across this, looking for hair suggestions for children I have coached. http://cute2tryhairdos.blogspot.com/ This site is fantastic, with some video demos and many ideas from simple to almost OTT. Many could be adapted for gymnastics. It seems this blogger has a lot of fun trying out all these hairstyles.
Our gym requires a bun for all girls on the team when we go to a competition if they have short hair that won't go into a bun then the front tied back and the rest slicked back into place so it doesn't move.
As for music talk with your coach and see if she/he has any suggestions for you. You need music that first you LOVE because you will probably have it for a few years and second isn't going to be overly challenging for your skill level thats where your coach can help. Keep away from Disney though it is way over used.
Floor music express and Energym both have great collections of floor music and you can hear some samples played. Energym lets you hear the whole thing and floor music express you only hear 30 sec of it unless you pay 20 cents (you have to spend at least $1). Good luck