If you're talking about MBA programs, you only want to pay to attend the M7.
The M7 include Harvard, Penn's Wharton, Columbia, Northwestern's Kellogg, Chicago, Stanford and MIT Sloan.
You take the GMAT for business schools. Scores, while important, aren't as important as work experience. A lot of applicants to the M7 have 750+s GMAT scores so you still need to get a decent score. But you aren't getting into an M7 unless you have good work experience.