What is a good protein/creatine to gain muscle and mass?

im 18 years old and would like a good protein to put on muscle and weight..i weigh about 150 but im in good shape and im tall so it looks like just skin and muscle. i want to gain weight and muscle and actually keep the strength. i go to the gym about 5days a week working on every part of my body. expecially upper body since im small there. im not looking for the most expensive stuff out there. something you can buy in your local gnc and to be legall. thanx