Eating right, as others have said is the most important thing you can do while building muscle. However, a little extra help in the form of protein and other supplements does not hurt. I use
http://www.supplementwarehouse.com because they will beat anyones price by 5% instantly! I just went on google shopping, searched for the sup I wanted, found the cheapest price to a website I would never order from, and they matched and beat it.
I've used three different kinds of protein in the past couple of months. Dessert by BSN is great tasting but expensive. Body Fortress whey does not mix nor taste as good but it is very cheap. Like $13 for 2lbs cheap. I just bought 2 lbs of 100% whey by Optimum nutrition. Good taste, super easy to mix up and price is not that bad.
If you are looking to gain weight, check out muscle milk. Big caloric value per serving with tons of protein. Check out thesupplementrating.com for reviews on just about everything out there.
I would also recommend getting some creatine/glutamine. I take vassive ce right after my workouts and it has really helped me to recover fast after some intense lift sessions. The good thing about vassive is that it is no load and mixes/tastes great mixed with just water.
Oh and one more thing, pre workout igniters like no xplode have no affect on me whatsoever. There is a multitude of people out there that insist they improve their performance but I just get a little rush of energy and that's it.