Post workout drink advice/ Where to buy supplements?

I plan on buying Designer Protein to help with my calorie and protein supply. But what should I take after I workout? I heard that carbs is most important at that time.

I saw this drink in the store that had like: 380 calories, 35g protein, 60 g carbs, but its 3 dollars a bottle.

Does someone know of a supplement that is comparable and cheaper? Whats a good site to buy supplements from? I think GNC and Vitamin shop are overpriced. Thanks