Some places should have dekes on clearance soon as the season is coming to an end. Check your non-hunting "specialty" stores like Ace, Kmart, etc. Wal-Mart was selling hot buys last week for $15 per dozen, although I wouldn't touch a hot buy with a ten foot pole. For ducks and geese I use all G&H dekes. These are good quality, last a long time, and look realistic. Unfortunately, they aren't the cheapest. But if you are just starting you could go with something cheaper just to get a spread started. I have hunted over some really old decoys that had almost no color left on them and did just fine. Being in the right place is more important than having the best looking dekes. As for species, around here you will find a little bit of everything depending on what part of the season it is. This year alone I have seen many mallards, pintails, redheads, goldeneyes, buffleheads, gadwalls, green and blue winged teal, widgeon, canvas backs, spoonbills, and bluebills. All of your puddle ducks and some of your divers will decoy just fine to mallard decoys. Having different species of dekes might help but to start out I would just go with all mallards.
As for calls, I have found that a call is not something you want to be cheap on. I have gone through a lot of cheap calls and didn't really know what I was missing until I finally got a decent one. You can get some good sounding calls in hard woods like diamond wood and cocobola for a fair price. I have an Echo Timber in cocobola/poly that I got for $45 and it is worth every penny. The good thing about the nicer calls in the displays at stores is they aren't in packages so you can blow them to hear how they sound before you buy them.
For waders, I like my Cabela's breathables. They are nice and cool for those 80 degree days but still warm enough with a couple layers of clothing on those 0 degree mornings. My brother has the real thick neoprenes and he gets too hot on the hot days.
Another thing you will need is a camoflauge jacket. To start out with, I would look for something light and waterproof that is a 1-2 sizes larger than you wear. This way you can wear it in any condition and be comfortable. You can wear it over a short sleeve shirt on a warm day or wear it over 5 layers of shirts in sub-zero temperatures.