A drake whistle and good decoy spread will get it done a lot of time in the duck parks with tons of pressure. Getting started, I liked the buck garner calls. When I started, I got a buck Garner call that came with a cd and a drake whistle to learn from. I upgraded from there, but don’t think it was absolutely necessary to do so.
A lot of guys say the double reeds reeds are easier to learn. I don’t really see much difference between learning on a single reed or on a double reed, personally. Perhaps the double reed calls give a bit more resistance and back pressure?