No shotgun and
no-xplode are both nitric oxides but from different companys,
cellmass is a creatine ethy ester and is usually stacked with no-xplode although bsn are under trial about both of these products.
You dont need to buy everything from one company which it seems you are doing, but if you do then imo chose optimum nutrition. They have a good choice of products, excellent quality and are reletivly cheap.
Try to stick with a basic stack of,
whey protein
creatine monohydrate
a multi vitamin
fish oil or flaxsed oil
You can then add in one or all of these if you wish,
BCAAs
glutamine
Nitric oxide