You'll need:
Two pairs of jeans
Two black skirts
A pair of gray or green pants
Knit T-shirts in assorted unobtrusive colors such as: black, black, black, dull green, liver
Socks (preferably striped or with cunning little animals on them, for flair)
Five pairs of Converse in assorted colors and styles, six pairs of $100 Fluevogs and/or Campers
Now:
Mix and match the above, hoping that the unremarkable nature of your wardrobe will keep people from realizing you're actually wearing the same five or six outfits over and over.
Wash at least two loads of darks a week.
Keep the $100 shoes in your closet most of the time because they don't really go with anything else you own.
Spend all the time and money you save on beer.
Bonus: Be sure to whine a lot about how you don't have anything to wear. There is nothing--nothing!--that will make you more attractive than complaining about things that you can easily fix but choose not to.
That's all you need. Now get on up and go on with your drab self! (Tee hee!)