There is nothing to buy once you get to the higher levels. Perhaps you can use experience to 'purchase' attributes such as higher HP, elemental resistance, physical resistance, etc.?
OK, SO I HAVE BEEN RUNNING AROUND SHAKING TREES FOR (literally) HOURS AND CAN'T GET A DAMN 5th FOX. WTF? INCREASE THE DROP RATE!!!!
I'm now going to give up and not bother to finish the game.
 "My Pet Protector 2"){kind=icon}
 "Anti-Idle: The Game"){kind=icon}
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 "Stones masters"){kind=icon}
 "Crunchball 3000"){kind=icon}
 "Bunni: How we first met"){kind=icon}
 "Zilch"){kind=icon}