How can I improve my extra-curriculars to get into a decent college or possibly an Ivy League?

Answered

Since you are a sophomore, you should use this year to do your extra-curricular activities now as opposed to in Junior and Senior year where you would really want to focus on your classes and maintaining a strong GPA (which is one of the most important things that unis look for), and also getting a good SAT score. With all of that going on during your Jr and Sr year, extra-curriculars will be something that might be difficult to manage because of that stress (unless there is something you are really passionate about, or something that you are a leader of (like your Sustainability Club).

Back to the question,

I personally think that you have a pretty good range of extra-curricular activities already, but don't add more or join any more clubs. Rather, try to get more authoritative positions in the clubs you are already in because colleges don't look for how many clubs you were in, they look for ones that you excelled in and were succeeding in.

For example, in Model UN, try do something that you previously have found difficult or hard and build on the skills on that, rather than attempt every position possible.

I hope this helped you!! :)