I disagree about IPAs being easy to screw up. Hoppier beers tend to be more forgiving of little mistakes than say, a pilsner or a blonde ale. As long as you don't make it cloyingly sweet or go overboard on the bittering hops without any flavor/aroma additions, you'll be fine.
As the others have said, about 6 or 7 lbs. of light DME will give you a good malt base, along with 1/2-1 l. of light crystal malt for color. If you want to mix it up, substitute in a few lbs. of wheat DME for a wheat IPA, or switch to a darker crystal malt with 8-10 oz. of Carafa III for a black IPA.
For hops, try a 60 min. addition of 1-1.5 oz. of high alpha acid bittering hops, and later additions around 30 min, 15 min, and at flameout. Like sweed said, Citra, Amarillo, and Simcoe all work really well for late additions.