It is impossible for an economic discipline not to understand mathematics, so calculus, linear algebra, probability theory and mathematical statistics are all necessary.
Moreover, the basic or core courses of economics include: political economy, microeconomics, macroeconomics, history of economic theory, econometrics, finance and statistics, so it is relatively easy to learn mathematics well and write it after reviewing, and English must be done well.
Personal suggestion: there is no need to carry the burden of postgraduate entrance examination now. It is urgent to learn undergraduate course well. If you get good grades and get a postgraduate qualification, why not? After systematic study, I will consider taking the postgraduate entrance examination in my junior year.