2 cups for small people ie: children, or small women
If you are a big grow man, 4 cups. It is a lot, but the stuff is so inexpensive.
If you want, try 2 cups and see how that goes. Next time, if you did well, add more.
I do want to mention one thing; however, if this is your first time, I want to worn you. It will make you feel very relaxed. If you are not familiar with it, it can make you a bit uneasy.