I need to gain weight. I'm 128 pounds. No matter what I eat I can't gain an ounze of weight. I am totally ripped but need to put on about 15 pounds. muscle..not fat.

suggestions on what supplement I should use. not concerned about brand..just what to use. protein isolate....creatine...I need a refresher course becasue I haven't worked out or taken suppliments in years. How much have things changed?