All transactions in Dungeon Defenders II are between the player and the platform provider. Please refer to Steam Support, Xbox Support or PSN Support for any refund request so they can take appropriate action but please be aware that there is a no refund policy in place.
Should you have purchased an item or bundle and you have not received it in game please go ahead and try the following solutions:
1) Log out and back into the game
2) Check your in-game mailbox for any content
3) For gems check your balance, they will be credited directly.
Should you not receive your items after these steps please go ahead and file a support ticket and provide a picture of the transaction in question. We'd be happy to investigate!