RE: choosing a diaphragm call
Everyone has their favorite and thats cool. You should try any call at first just to get used to it in your mouth. Then try to get sound and then work on getting good sound from that call. After you have done that try a couple different kinds and manufacturers and see what you like best.
Don't be afraid of the ones with fancy cuts as they give the most realistic sounds. Once you get them figured out!!!
Give the River Valley X-rated a try as that is a big seller.
Good luck.