I was in your same situation many years ago. Here's the basic things you will need. Once again, just the basics...

12 mallard decoys, water keel. $35
12 anchors (old spark plug, washers, etc. nothing fancy). $5
12 decoy anchor cords, about 3-4 feet long, $5
mesh laundry bag to carry decoys, $5
hip boots. $50
camo outerwear, hat, gloves. $75
a mallard duck call, $20
3" steel shot, #2, $15/box


You can upgrade by getting 36 decoys, a 3 dozen sized decoy bag, chest waders, a boat and motor, spinning wing decoys, etc.