It sounds like you are on the right track. A dozen decoys is plenty for most places in Az. When you have more money...Buy more, but a doz will work for now. Remember to leave enough room between dekes for the ducks to land, also remember, most of the time the birds land into the wind.
Practice calling everyday, the more you practice, the more you will sound like a duck. It is a good idea to include some sort of duck whistle on your lanyard and incorporate it with the quacks, I think it makes the ducks a little more comfortable and willing to commit. But don't call too much, as a general rule, call to the wingtips and tailfeathers, not when they are coming in.
Good luck, another site with great info is The Arizona Sportsmans Journal www.azsj.org