my trainer said I have to drink protein shakes to build muscle, that is how the pros do it. he had several brands at the gym on display and he told me i had to pick 1 to use daily and a month's worth is $120. this seems expensive and when i asked him why he got mad at stormed out of the office and said to do what i tell him. so now I gotta pick 1 to use and what should i look for?