Should I go into a masters program?

Hello, I am a junior economics major at the university of Michigan. My dream career is going into sales and trading.
I have had only 3 sales and trading interviews with top IB, and to be honest, I lost them because of my lack of networking, knowledge and competition with Ross Business School Students.
So, currently I am stuck, with nothing this summer. What should I do? Should I get an easy finance internship that has NOTHING to do with sales and trading or just study really hard for the GMAT and go to get my masters in finance or management at a top school.
Also what are the best schools to get my masters in if I want to go into s&t?