I battled Imperial for Gaius, took me more than 300 battles, I just didn't count it. All i know is that I definitely got around 40k MGP by the end of it all.

Moogle Mog took only about 7 runs.

Garuda took me fighting Marcette about 50 times, not including about 11 HM runs I did.

Those are far and away my most painful experiences so far, but I'm missing a lot of dungeon cards still... i just don't like grinding them all at once, really burns me out.