Your SAT score should be fine for TAMS, I think the average SAT score for my class was a high 1300, so you are right in the center for that. Outside of school, I meant things that do not directly relate to your classes. For example, I founded 2 clubs because I wanted to share machine learning with my peers, and also my culture. I also was a member of the debate team and a bunch of other things. I would recommend you take part in clubs or make your own. TAMS really likes people that make their own clubs. You could also do math olympiads for example. Volunteering is a good start, but if that is the only thing you do, that may not bolster your application enough.
I am sure TAMS will realize your school does not provide ranks, so not having won’t really matter as long as the grades themselves are decent.