Tell him to ditch the NO2, use that money to purchase a variety of quality proteins, thus avoiding the problem some have where the body adapts to one type. So he can "cycle" protein powders.
I did not jump onto the creatine ship until later in life, and I, for one, do not believe it helps one gain any "real" size. But it did help my lifting some.
Tell him to up his eating, perhaps show him some Berardi eating ideas, work on quality foods like chicken and vegetables - avoid the fastfoods and cokes.