These wonderful AM brothers already have you covered.
As you hopefully already knew, diet and training is the biggest thing.
Honestly no supplement will make "gains go through the roof"
If someone tells you that they will, welcome to the world of marketing
That said this is a supplement heavy board of course, all of us are here because we believe in the products and trust me none of us are fans of spinning our wheels lol.
Nor are we fans of lightening our wallets (well, most of us...)
I will agree with Jiggz above, creatine is something that is strait up unquestionably worth the value, adding it into your routine will help.
I too wanted to suggest my standard first product suggestion now which is Ergonine.
http://store.lockoutforums.com/index.php?main_page=product_info&cPath=3&products_id=2005157
(save with code: anabolic05)
I've linked you to the Nanaberry because that is a flavor experience everyone has to have
For under $1/day you can be getting 9 of the best, most proven Ergogens around. Ergogens being things that improve physical performance.
Many of these also carry secondary benefits to body composition, with proven effectiveness in fat loss and in lean mass gain.
This would cover your need for creatine, as well.
1 scoop a day and you will be trying out many of the things we strait up know work