As far as being involved and intelligent, don’t think that you’re in any way limited by your current status.
Be outgoing, play sports, go out with people, and do generally everything. I believe that grades don’t suffer when you have lots of extra-curricular activities, but actually tend to get better (or stay at a high level).
Join everything, talk to anyone, and play sports. The whole “clique” idea is absurd. There are no geeks, there are no jocks.
Can I be the first to suggest you completely ignore this advice! Socialisation is at least as important as grades - not for the individuals you meet (and not necessarily for those you befriend) but because it teaches you how to function in society.
Clearly, if you can get through as hostile as environment as school you can probably function in society. If you were to lock yourself away and just focus on books you’d probably be very unhappy as well as socially maladjusted!