At a minimum, you should have calculus I and II.

After that, a semester of stastics or econometrics would be important.

From there, it depends. If you are really interested in mathematical economics or mathematical finance, you would want to to take calculus III, and an introduction to ordinary differential equations.

For graduate level work in economics you might take real analysis, and perhaps linear algebra. Graduate level work in mathematical finance would require some knowledge of probability and stochastic processes.

Calculus, most definately!