On the less expensive end, you can use NOW Gelatin that is usually found in the baking section. It comes in a 1 lb bag for around $14.00. Other brands include Great Lakes and Bulletproof collagen powders that can cost around $25-$28.00. Gelatin and collagen are essentially the same. Gelatin is hot water soluble and collagen is cold water soluble. You can mix the gelatin in cold water and get more of a thicker shake.