Most will tell you a box is the easiest to learn on, I build box calls and will have to disagree. Its my opinion that a good sounding slate is more readily avalable and will put the right sound, to that gobbler and in you. I don't think production boxcalls for the most part are realistic Turkey. Of course the right Gobbler on the right day will fall for a nail and a rusty bucket. I aint that lucky thow.
Rent a few vidios, don't swallow everything they're sellin. Most get too agresive for my liken, but will be helpful in getting the proper sound.
Most important, DON'T PRACTISE ON THE BIRDS BEFORE SEASON.