I wasn't aware they added the other gems and the master guild tab, since I don't get on this often. Since you only get the luck gems from rebirthing, is there any reason not to rebirth instantly? I've done it a few times and how many levels you got cleared or girl level total seems irrelevant (unlike regular gems) as the amount of luck gems you get just keeps going up each rebirth.
Is there some hidden health bonus to enemies or something?