Personally I'd go with one size up from recomended unless you're going to double anchor.
http://www.basspro.com/webapp/wcs/st...006000_225-6-0
Buy galvanized or zink coated chain at Home Depot, 25' should be more than enough
Get at least 2 of these to attach the chain to the anchor and the rope to the chain.
http://www.basspro.com/webapp/wcs/st...006000_225-6-0
Finish that off with 300' of 1/2' - 5/8' polypropoline rope and you should be set for just about any conditions you'd consider staying on the water in. Can you get by with less? Of course, but would you rather have it and not need it or need it and not have it?