Disclaimer: I have no first-hand knowledge of grad school admission as I'm myself an undergrad math student, but since you haven't gotten many responses I'm just going to pass on some of the advice given to me.
Do you have any hobbies? What makes you stand out from all the other people with great GPA's?
From what I've heard hobbies matter VERY little to grad school admission. Unless your hobby is very relevant to your major, but I have a hard time thinking of such a thing for math.
From early introductory courses like these it's impossible to tell if you are on the right path. Courses like linear algebra and calculus are expected, proofs is meaningless as you're expected to be able to do proofs whether you have taken a course or not. Ordinary differential equations and number theory seem like interesting electives, but ultimately I doubt they would affect graduate admissions. This does not mean that you have necessarily done anything wrong, just that graduate admissions is more focused on the later and more advanced courses that tell them what kind of preparation you have and what kind of courses you can handle.
The best way I guess is for you to consider what kind of courses you will have taken when you finally apply for grad school (you should have, or be able to make, a rough plan of what courses you'll take). Ideally you should have taken (or be in the process of taking) quite a few of the following:
- Abstract Algebra
- Complex Analysis
- Functional Analysis
- Topology
Especially algebra I suspect would be important. I cannot tell whether the courses you're taking are especially hard as I don't know your preparation nor the level they are done at. If you are able to do it, taking a few relevant grad courses would also be a great idea (but a good foundation is much more important):
- Homological algebra
- Algebra (your college probably have some sort of continuation of the undergrad course).
- Algebraic combinatorics
- Enumerative combinatorics
- Analytic combinatorics (not all these kinds of combinatorics may be available, or they may be under more specific names such as "random graphs" or "asymptotic analysis of trees").
- Algebraic topology
Are choices I would consider (I'm biased towards the algebraic side of math, but seeing as you're interested in combinatorics then so are you probably).
If possible, opportunities such as undergraduate research is always good, but it matters much less in math than in subjects like physics. In math you need a bit more of a foundation before being able to take a serious part of any research, and the admission committee knows that your professor may have helped you quite a bit. I would not obsess over undergraduate research and definitely value solid coursework higher, but if you see a perfect opportunity (such as a professor announcing he wants to take on some undergrads for some research) you should consider it.
