As per the intro tutorial, keys are a random drop when you click on any girl doing a private show. If you're really mashing those private shows you should have plenty of keys.

And yeah, got a x10 multiplier on the wheel. Not sure what the duration is on it though. (I've been spending rubies on increased replies, so I'll have a (sort of) stockpile when I get home/wake up.)

Got to 5, but the girl you unlock at 4 is peculiarly buggy. (panel doesn't ungrey to hire, but you can anyways, she wasn't in text listing at first after load the next day, even though I had replied to her a few times before closing the game out.)

Game also frequently crashes with a unity error about an uncaught abort when I try to log on though. Wouldn't be all that surprised if it's some sort of penalty for clicking too fast. There's no way I'm burning my mouse out on a game like this, so I have a repeater set for ~25 clicks per second, which isn't too inhumanely fast. (and admittedly helps with the surplus of keys.)