How do I go about making/getting a costume?

I am trying to get costumes together in order to cosplay the anime Death Note. I have looked on 'ebay' and 'google' and cosplay websites, however I am unsure weather or not I should buy the costume(and from where)and alter it, or make it myself. I am also unsure where to get the material to make the costumes. So, I am at a loss and in need of suggestions.|||Jo ann fabrics is really good at helping people out. they have fabrics and guides to making costumes and clothes and stuff|||For Deathnote it could be easy depending on wich character. Any of the human characters especially, just do to a store and look for cloths that resemble theirs. Simple. as for the death gods, that would be more difficult, a bit of makeup and fake teeth. some feathers or well depending on which one... hmmm... I've made a few costumes of my own, but they all consisted of people not demons or creatures or deathgods. If you are going for the deathgod you might want to purchase that one.