My daughter has been a serious artist since she was quite young, and went back and forth in high school on whether to study art in college. She was aiming for the need-based-aid super-selectives. At the time she applied, she had decided to do math after all, but submitted an art supplement that included work produced over several years. She had considered doing AP Studio junior year but decided not to because of the time factor and because she was leaning back away from studying art in college at that point.
And I hear what you’re saying about community service but just wanted to mention since I was commenting anyway that my very introverted kid, also a serious baker, did a yearlong project producing spectacular desserts every weekend, in large quantities, for an area soup kitchen.
You've received a lot of great advice here, but just want to mention Art of Problem Solving for books and online classes. Challenging, fun classes for competition math topics and also the traditional high-school math sequence, but at a much higher level of abstraction and rigor. https://artofproblemsolving.com/school
@vonlost, the critical asterisk to that definition of reach/match/safety is that no school with an admission rate under 30% can be considered a safety, no matter how high the applicant's test scores are.
You could create some extracurriculars of your own, finding a way to volunteer and create a program at an elementary school, volunteer at a social service agency, start your own dance studio teaching little kids.