You can always buy tons of gems + get an in-app purchase refund. It works, however you'll want to spend the gems prior to the refund.
The downside to this is you'll get a negative balance for the amount of gems you spent but keep all the shit you bought.
You may also have trouble getting into events, like you have a negative balance of -15000 you arent going to be able to buy anything with gems after that or pay for event tickets