When you create your City in The Godfather: The Five Families you will be presented with 10 starter Diamonds to assist you. You can use these Diamonds to purchase items in game that can assist you in battle or leveling up your City.
If you would like to acquire more Diamonds, you can purchase Diamond package.
Purchases on Kabam.com can be made with your credit card directly through TrialPay or PayPal.
Purchases on Google+ must be made with Google Play. If you do not already have an account it is possible to make one prior to purchasing Diamonds.