Everyone has a good point. Yeah, G&H are excellent decoys, but to get a start in duck hunting, they are not absolutely necessary. If you wish to have a quality decoy that will last quite some time, go ahead and consider some of those more expensive cork and /or burlap. if you buy yourself some GHG or Cabelas Hotbuys you might save a lil' more dough. Some people have even found great deals on internet auction sites. Oh yeah, don't forget the DHC classifieds. You can start cheap and build up over time. Furthermore, you might want to think about when you do your hunting, what kind of birds you have coming through. i.e.; divers, teals, wood ducks, etc. It never hurts to have several different species to add a little more realism.
PS: you have to think about anchors and cord too. Personally I'd start cheap and build up over time.