Westbucks and coins are in-game currencies that can be used to further develop your farm.
The only place where you can purchase Westbucks and coins without breaking the rules of the game is the in-game store. In order to successfully complete your transaction, you will need to open the in-game link by clicking on the plus sign next to your currency of choice, and following the instructions that appear. Purchasing game currency in any other location may lead to the permanent ban of your gamer account.