Graduate schools in economics require a strong underpinning in math for acceptable performance. You can always strengthen your math background after entering graduate school, but without the minimum preparation you will be at a distinct disadvantage.
In order to be competitive in getting into the top 20 to 25 graduate schools in Economics, you will need to have a strong math background. In addition to the standard Math 140 1nd 141, we recommend that you take several advanced level courses in linear algebra and calculus. In Linear Algebra, you should at a minimum take Math 220 (Matrices) and perhaps the more advanced Math 436 or Math 441. In Calculus, you should at a minimum take Math 230 (Multivariate Calculus).
To further strengthen your quantitative toolset, we strongly recommend that you take proof-based courses such as Math 312 (Concepts of Real Analysis). More advanced courses in real analysis include MATH 401 (Introduction to Analysis I), MATH 403 (Classical Analysis I), MATH 404 (Classical Analysis II).