I am a double major in mathematics and economics. Here's what helps:
Undergraduate degree in economics: calculus and an upper-level statistics course. If you really want to impress your professors with research, I highly recommend taking multivariate calculus and differential equations. Linear algebra is not necessary, but it will make life a lot easier. Fortunately, you don't need to be incredibly math-oriented to succeed in these courses (but they will make math addictive).
If you're looking to study economics in college but you'd also like to go on to graduate school, then it's vital that you take multivariate calc, differential equations, linear algebra, probability, statistics, mathematical modeling, and real analysis. In fact, many top economics schools will just check to see how you did in real analysis and calculus before looking at other grades.
If you're going for a graduate degree in economics, you'll most likely take partial differential equations, probability & statistics, real analysis, and maybe even stochastic processes, depending on what your area of research is.
The more mathematics you take for your economics major, the better quality your research will be; the better quality your research is, the easier it will be to be accepted into a graduate program in economics.
If you're not interested in academia, then taking a statistics course and calculus 1 should suffice.