Only thing that I would add, is that I think a box call is the easiest call to use and sound realistic on... The mouth call becomes an important call as you learn to call, but it is probably the most difficult call to learn to use, and to learn to use proficiently.
In my opinion, a decent box call is a must for any beginning hunter, and I still take one or two in my vest. Easy to learn, realistic, and loud....
Great point, Marc. Having a good box and/or pot call (also generally/historically called "slate" calls) are essentials for any turkey hunter,...regardless of experience or ability.
Too often, I think, beginning hunters watch turkey hunting videos and see most of those guys using mouth calls. Their inclination is to assume that is what they should be using. REALLY bad idea for most new hunters! Best advice for the new guys is to stick with the easy-to-use friction-type calls until you have mastered mouth calls (or any of the other more difficult to use calling devices).