Milk

You can collect Milk from cows in the Cow Barn. It takes 15 minutes for the cows to make the milk, and you can speed that up by paying with jewels. You can sell 1 milk for 4 coins, and that price goes up as you sell more and more. Milk is used to make a Strawberry Shake and all the items in the Milk Shop. It's also used to make other things, but those are the beginning items.