what is the best supplement to add muscle?

Just eat alot, I have used supplements and honestly the best thing is to eat constantly and lift regularly. If you do research then you will see all proffesional bodybuilders agree that its the amount you eat not the supplements you take. Also, you have to eat good. To build muscle eat lots of carbs and GOOD protein. GOOD protein is FISH, EGGS, soy, dairy, and other good amino acid foods. Now, something I would reccomend is Whey Protein. This is a fast metabolising protein which should be taken about half hour after a workout. Its helpful for people who cannot always eat protein but if you are serious about getting lots of protein and cannot eat enough because your body cannot handle it then I suggest Whey after workouts and Casein when you wake up and when you go to bed. Of course you also need to maintain your body with WATER, vitamins and minerals because without these muscles can't be built. I don't really suggest any other supplements like creatine or extra b12 pills or extra omega-3 pills because like I said, these are extra and if you eat well you don't need them.