Most of the time, orders deliver immediately. Occasionally, they may take a while to arrive. When this delay occurs, it means the purchase is still processing. No need to try and buy them again, they should arrive soon!
Sometimes, all your device needs is a fresh connection with the servers. Try exiting the game and logging in again, this may speed the process along.
If you still haven’t received a purchase made more than 24 hours ago, please contact iTunes support, as Apple process all payments made toward the game. You can reach them right here.