My favorite iPhone 5 case is the CM4 iPhone Wallet Q Card Case. This case claims to hold 3 cards, but I’m only comfortable keeping a credit card and my driver’s license in it. It securely holds these two cards. I think 3 cards would be secure, but I think they would stretch out the leather. Some people worry about losing “everything”, but I see this as only having to keep track of one thing.
When I need to carry cash or additional cards, I grab my old Kenneth Cole REACTION since it is a pretty slim bi-fold wallet.