protein shakes r fine but shouldnt be your only source of protein. many people use them because geting 300-400 grams of protein a day from food is tough to do especially when you have school, work, sports ect.
as for the no2, wouldnt really advise using it, its not that its bad for u, it just kind of a scam and costs a shit load. a pump isnt what gets you big, ya it feels cool when your in the gym but doesnt ammount to anything after your done working out. heavy ass weights, compound movements and lots of food is what gets you big. that money your spending on no2 could be used much better if you invested in a good multi vitamin and some creatine ethyl ester or some of the new forms of creatine.