Which SAT II tests should I take!?

It's tough because you're in IB, and SAT Subject Tests really tend to favor AP students since the tests are made by the same company and thus the questions on the AP are similar to the subject test and vice versa. Needless to say, you should try and take subject tests when you've reached the highest level that you're going to get to in that particular category EXCEPT with Math and English. As I stated above, subject tests tend to correlate to AP's, so if you haven't take an advanced English Language or English Literature course, I'd caution you against taking either one for a subject test. With Math, taking it when you've just completed trigonometry is actually the ideal time because that's the most advanced material on the test, and if you continue on to calculus and what not, you're going to start forgetting more and more of the basic algebra, geometry, and other basic concepts that you learned years ago, making it more of a hassle to have to restudy all of this and more likely that you'll make basic mistakes simply because you haven't had to do the work in a while.

The thing about Math I versus Math II is not that one gets you less credit at some colleges, but that Math I is not always accepted as a subject test when used to fulfill a requirement for subject tests are some colleges / universities, so Math II is the safer blanket test so that regardless of where you apply, you know for certain that it'll be valid for submission in the admission process. Math II is a lot harder, but the curve is also a lot stronger (13% of students get 800, a rate higher than everything except foreign languages, which can be explained by merit of native speakers).

I actually don't recommend taking SAT II's until Junior year. By then you'll be smarter and probably perform better. Also, you should take math 2, not math 1, because math 1 is really really easy and therefore doesn't get you as much credit with colleges.