Buddy Bucks is the currency used to buy common items, earned by harming Buddy in various ways. Some items give you more bucks, while some may give you less. Although the easiest way to earn bucks is by purchasing some using iTunes/Google Play money. It appears in the bank and Buddy will say, “Show Me Your Wallet!”
To get lots of money, buy the gas nozzle (cost 4500 bucks) and then buy the pencil gun (cost 49 gold), then fill the buddy up with gas, count to 8 when buddy makes sounds when trying to talk, once you've counted to 8, get the pencil gun, and shoot him, you will get LOTS of money!