You need 3 letters at every school I know of.
Nobody here can answer your question (what level of schools), especially not with the amount of information you have provided. There are absolutely hellacious, brilliant students at great schools, as well as complete dullards at worthless schools who have a "3.85 GPA at an American university."
You need to talk to your professors.
Here are the generic facts I can tell you: Admittance to graduate school in pure mathematics is extremely competitive. It's grown even more competitive in recent years (it's possible your professors aren't really aware of this, so carefully evaluate any advice they give you, but they should still be your best resource). Letters of recommendation are extremely important: it matters that your letter writers are substantial mathematicians and that they are very positive about you. Having a lot of advanced courses on your transcript is also important.
If your profile right now looks like "Pretty good GPA from a pretty good school with a pretty good GRE score and decent recommendations," then you need to know that the best schools (say top 20ish) will each have 200 applicants with profiles better than yours.
Things are quite different at lesser schools (say, below top 50ish), but here's the thing you need to know that people don't usually say outright: a PhD from a "top 75" school is a very different thing from a PhD from a "top 15" school, and is very unlikely to lead to a professorship at a good research school. (Please understand that when I say "top 50" or whatever I'm not endorsing any particular ranking of schools or even intending to imply that there can be an accurate ordering of schools; this is just the best way to get across the point.)
I'm sorry if this sounds negative, but I think you should have an accurate view of things, so that if you decide your current situation is not going to get you where you want to be, you can take stock and figure out what you need to do to get there.
Talk to your professors.
