When starting GM mode choose your brand (either RAW, ECW or Smackdown).
Edit the available roster and all the superstars that aren't in your brand you can turn all off, but leave superstars with low popularity and/or divas. But remember not to disable one of your own stars.
Then choose not to draft and just stick with the default roster.
Then all you have to do is preset matches, I got more than 8,000,000 fans this way.