Ok so A) don't get muscle milk. it's heavy metal count is much higher than other brands and that just fucks with your body
B) if your not serious about gaining weight don't bother with the shakes. Because taking one serving there is going to do nothing for you.
If you are serious your generally going to need to be consuming your body weight in grams of protein.
I was 149 at 5'11 and I started with taking "Serious Mass" by optimum nutrition, has something like 12 hundo calories per serving with water and 16 with milk. It's great if you can force yourself to drink at least 1.5 to 2 servings a day. but it is allott to consume. other good news is is fairly cheap but if your consuming a couple servings or more a day it can go quick.
With that and a hard hour and a half work out 5 days a week i made it to 157ish pretty quick. with 50g of protein per serving it also knocks a big chunk of that 160 or so you need each day(or whatever your weight may be)
Currently I take BSN true mass. It was cheaper than it is now but its got 48g protein per serving but only 630 calories. the nice thing is the serving size is about half the size of serious mass so i can do about 3 servings a day, one mid day, one post workout, and one before bed. I'm currently up to 168lb. in a few months with some slow weeks where i missed workouts and didnt eat right
but again none of this will really help if you don't dedicate yourself to your workouts and eating right as well. A combination of a high protein healthy high calorie diet with the shakes will put muscle on you real quick.
it's really about where your starting at and what you want for results and how fast. if your a skinny hard gainer like i was than the extra calories could help if you can force yourself to drink it. if your not a hard gainer something with less calories will provide a cleaner bulk with less fat.
www.bodybuilding.com
they have super fast shipping great deals and if you buy in bulk,(a couple tubs at a time) and spend over certain amounts theyll throw in free gifts like, t shirts, shaker bottles, all sorts of stuff. good luck if you have any question I can try to answer them for you