Welcome to RIU.
Don't mean to harp on you, but honestly, you should really do some homework. Although growing is easy, it only becomes easy after a lot of research. It isn't as simple of just running out, spending $400, and throwing the seeds in soil.
You need to know what type of grow you're going to do, you need to understand the differences with lights, ventilation, pH, temperature, humidity etc.
For seeds, I usually order from
http://mjseedscanada.com or buy locally from a couple organic farmers.
Take a read of the stickies in the 'Newbie' section of this site, then check out "The Basics" over at
http://growweedeasy.com
After that, you'll have a much better idea of what you're looking to get out of this, and will be better able to wring every dollar out of your budget efficiently. You'll also be equipped to ask more specific questions. Most people don't have the time to outline a setup for you in its entirety
Happy growing!
-spek