LogFAQs > #966442464

From what I can tell, it's actually physically impossible to get anything above a 2* gem in the game without spending money. If it was just campaign based it wouldn't be a big deal, but PvP is a big aspect of the game. There's a bunch of videos out there of people maxing out their characters as far as they can, then jumping in a PvP lobby and their entire team getting wiped by a whale in under a minute.