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.
We hired someone to work with my D on her common app essay, and paid about $1000. When we finally saw the essay – parents weren’t allowed to until the student and consultant thought it was done – it was clear that the help had been worth it. The essay passed the backpack test (if someone found a backpack on the street with this essay in it and no name attached, would they know who wrote it) in spades; I don’t think another kid on the planet could have written it, it was so specific to her. Some magic was worked in helping my D to summon those thoughts and connections and get them on paper.