there are a lot of supplements out there too buy. rule number one is never buy anything that is GNC brand. it all sucks.
if your looking to put on weight i suggest taking creatine. it will help your body hold more water and it seems to make me more hungry.
i take Cell Mass. its not a heavy dose of creatine by any means and it is a good creatine supplement to start on.
if your also looking for a protein/weight gainer i would recommend either True Mass or Muscle Juice. both are very good. I use muscle juice because it mixes much thinner and tastes great. if you are just looking for a straight whey protein i would recommend syntha-6 or freak fix if you want it in the powder form. and if you want the pre-made drinks nothing can beat muscle milk or myoplex.
as for NO xplode... when i used to take it i felt it made me more focused and made me lift harder. i stopped taking it because i have high blood pressure so i tried to cut the caffeine out of my diet