My old hs team didn't do competitions, but for games we were allowed to get out of class one hour early to prep for the game.
We would go to the commons area (the main part of school where everyone would normally be) and we'd make banners for the football players to run through at the beginning of the game which was always fun to make. Then we'd make goodie bags/ "Good luck bags" to give the football players something to show appreciation, and to wish them well for the game, they actually appreciated it!
The bags would contain a Water bottle, a healthy snack, and something football related like stuffed football, or key chain football, just cheap stuff like that.
We would practice any dances we needed to practice, and then we would do a "ritual" type of thing in a circle that was really cool. Then we got a blank sheet of paper, and wrote down positive things about each of the girls on the team, and gave it to each other to help them get rid of nerves and stuff, and it worked for us. A lot of this sounds so corny lol, but it really helped.
We were also a very spiritual team All of us were either Catholics/Christians so we def prayed before games :)