International Student General Help

Hey so I’m an international student, a junior currently studying in the UK for my high school life (after previously living in two countries prior to this), and since I don’t have many resources to aid my goal of getting into an ivy league school (primarily Columbia), I was wondering about some general facts/statistics on international admissions, and what extra curriculurs/commitments I should think of getting myself into now?
I’ve been reading some threads on CC and found that getting involved in a lot more extra curriculurs beyond what the school offers has been common throughout accepted and rejected applicants, so are there some ideas that could be suggested for me to start on that aspect of my application?
I’ll probably have some other questions as I go along, but that’s all for now. Thanks a lot.