Here is my smoothie recipe, which I make everyday and take it to work with me:
1 cup of dry rolled oats
1 cup of water
2 scoops of whey protein ( 50-60 grams )
I soak the oats in water overnight but I don't cook them. In the morning I put everything in the blender. If the smoothie is too thick I adjust it by adding a little bit more water.
Simple, easy, healthy and cheap to make.