1. The easiest way to get Farmville Farm Cash is by leveling up. Each time you level up, you get $1 FV Cash
2. There are other ways too, like completing 'free offers' or buying Farmville cash with real money.
If you want to earn farm cash by leveling up, look out for ribbons. These are the best ways to increase your coins, XP's and become a high level farmer.
It also ensures that you get FV dollars & cash pretty quickly.
Source
Farmville on Facebook - Level Up Game Secrets
