if you are truly looking into supplementing right, here is my advice...
first forget gnc exists, order online and enjoy saving money. there are several store sponsors on this site that are good, other good sites are bodybuilding, bulknutrition, dpsnutrition, discountanabolics etc.
next your diet and routine are more important than any supplement. if you are looking to bulk, aim for 1g of protein per kg of body weight. cals should be 500-1000 cals above maintenance. 40% cals should be from protein, 40% from carbs, 20% from fat.
get a good protein, ON and dymatize are cheap, gfpro, isokool and sustain are delicious.
get a good creatine, if mono works stick with it, if not xceed, clout and sizeon are all good choices.
cellmass is also a good creatine. no-xplode is a preworkout energizer and in my honest opinion is more mental than anything. you'd be better off getting an eaa + carb drink pre workout [8-beta anabol, all-in-one, vendetta] studies have shown this to be very beneficial towards muscle growth. post workout whey + carbs is also proven to be beneficial [replenish, aftershock recovery, anator, myozene].
good luck!