Nowadays there are two ways to undertake research on Finance. One is so-called Theorism and the other is Empiricism. If you want to focus on Theorism, you have to build up your mathematics, especially Stochastic Process and Stochastic Culculus which are the foundation of Options Pricing Theory. Nobel Laureate Merton Miller said that the future of finance is on Options. If you like Empirical way, you have to improve your econometrics, especially Time Series Analysis, which requires strong background of probability theory and statistics. Anyway, if you want to step further on the way of finance, mathematical tools are indispensable. Hope my comments useful to you.