Hi,
Yes you can apply for MA economics after doing ba from economics and maths.
Minimum eligibility criteria required for masters degree is 55% aggregate in bachelor's degree program.
Here are some of the good colleges in which you may pursue the degree-

Delhi university

University of Mumbai

University of Hyderabad

Jawaharlal nehru university

Jamia milia islamia university

Banaras hindu University

Hope it helps...