I believe your question is: "Should you go for your MBA?" - Anywhere from 2-4 yrs of industry experience is ideal for applying. As a math major with your background, you would do best by making your GMAT stand out to compensate for your "average" academics. Most important will be your GMAT verbal score since on paper you are a math graduate working at a bank so adcom won't question your skills in that department as much.
So focus on preparing your GMAT verbal as much as you can and make sure you are wary about any potential "stupid" mistakes you might make on the quant section.
Good luck on your preparation. We are here to help.