A gift of an empty wallet is definitely bad feng shui, it symbolizes the recipient will never have enough money.
I wouldn't see it as necessary, but it would be really cool!
Just put in monopoly money or some extra change and you'll be good to go.
Where i'm from they say it's goodluck to put a 1 penny piece inside.
It used to be considered good luck to put in a dollar or whatever when giving a wallet.