<p>Take some of both. But taking graduate economics classes is probably what will help the most and what you should find to be most interesting if you are interested in economics. Best combination would be economics, math, statistics, and computer science, but that’s not practical. Some people say take math plus psychology or math plus philosophy but why do that if you are really interested in economics.</p>
<p>In microeconomics, calculus on matrices and optimization theory is important (what it means for a matrix to be negative semi definite, the implicit function theorem, young’s law, etc.) Real analysis is useful here, especially in regards to properties of functions. </p>
<p>In macroeconomics and asset pricing (finance), dynamic programing is what is used a lot so use differential equations, ordinary, partial, linear, and nonlinear. Majoring in physics would probably be good preparation and there are a lot of economists who were physics majors in college, after all physicists are the ones who invented differential equations. Stability of systems of differential equations gets used a lot. Dynamic programing also uses functional analysis, functional operators (like the bellman equation). </p>
<p>In econometrics, linear algebra is important and you want more theory than whats in a intro type linear algebra class (ex. properties of a positive semidefinite matrix). Statistics would be important here too obviously. You want a statistics class that uses calculus, like CDF = integral of PDF and expectations using integrals.</p>
<p>Game theory uses a lot of high level math in the existence proofs. You don’t need much to solve simple games but that’s not what game theory is really about. </p>
<p>In math there are theorems called fixed point theorems and these are important for proving stuff about equilibria, which is a lot of what economics is about. </p>
<p>Knowing about probability theory is important for all of these topics. </p>
<p>Like anything you can always know more math and statistics.</p>