When my gymmies dressed as gymnasts for Halloween one year, they wore matching warm ups (any track suit would work. If it is a little oversized, that would be fine. Both girls wore the same size warm ups ... OG was 9 and YG was 6. YG rolled the waistband down like she saw the "big girls" at meets do). A body suit or a form-fitting tank top tucked into the pants would substitute for a leotard if you didn't have one. Then you just need a cute hair style and scrunchie. Good luck.