Alright, so I have the money to order some or go to my local GNC. What should I look to buy and how much should I spend?
i would ask someone that works at GNC. they're SUPPOSED to know what they're talking about. some key points, IMO:
protein shake - find one with at least 30-40g of protein per serving. i've tried a few different kinds and haven't had one that tastes HORRIBLE, but avoid cherry or grape flavors, IMO. and like i said earlier, muscle milk is one of the best tasting protein drinks out there.
calories - you need to intake a surplus of calories to really gain muscle. note the caloric content of these drinks. it's good to eat more to get extra calories, but you have to be sure to consume "clean" calories...so avoid heavily-processed foods with high-fructose corn syrup, sucrose, trans fats, other nasty stuff.
fat/cholesterol - some shakes have a high level of cholesterol or saturated fats. ask about this as it's often not as it seems. muscle milk, for example, is hight in fats, but they are "designer fats" that actually help you burn body fat.
creatine - don't bother with the creatine monohydride unless you want to have water-logged, puffy muscles. (it does increase your size, but it's not my cup of tea) go with creatine ethy-ester. it'll give you a leaner, more toned look. it's expensive though.
NO2 - nitric oxide. increases blood vessel size temporarily to deliver more blood, oxygen, nutrients to your muscles. very good to take BEFORE a workout to help you lift heavier and longer. works well stacked with creatine because it helps to get the creatine to your muscles.
NOTE: many protein drinks also have NO2 and creatine in them. this is good if they contain pretty good amounts of each. usually, however, separate products will be needed to get sufficient quantities.