Originally Posted by JMich

There's not much stuff to actually buy, other than N Tickets during gambit for the pink keys. I'd suggest to keep some pero in reserve (if you need to level a card quickly), but other than that, do with it whatever you like. For example, I'm currently spending mine feeding the rat voting tickets, one at a time, hoping for candy.

Don't forget the elixers and potions during Elite Guard! I generally spend about a million and a half on those during the event (and still end up with more pero after >.< )