I can use diaphragm calls, but my go to call for many years has been a Lynch World Champion box call. Sometime I use both in conjunction with each other, one advantage of the mouth call is restricted movement when they are close. I only wear woodlands camo for both turkey and archery hunting, no need for the latest and greatest, a head net also should be worn along with camo gloves.
Master the yelp cluck and purr first, I have shot many a bird by answering with just a cluck after getting one to gobble using yelps, when you get one to answer a call he knows exactly where you are, be on high alert and ready toward the area you heard the gobble, he may gobble more as he's coming in in which case I answer with a cluck or a short yelp if he's still at some distance, or he may come in silent.
Read all you can on hunting them, I sure as heck couldn't win any turkey calling contests but I somehow manage to call them in.
The 3 closest gobblers I ever had to me I never got a shot at, I was aggressively calling another gobbler and they came in silent behind me, then they gobbled and I almost jumped out of my skin, amazing how they seem to be able to put a tree between you and them as they run off! #-o :lol:
Another point, I usually aim for the base of the neck, if you aim at the head about half of the pellets are going over the top of it unless it's really close where the pattern is more dense.
It also doesn't hurt to pattern your gun, you might be surprised at how much difference there is in the pattern between shells, chokes, or where the main concentration of pellets is compared to the aim point. I never did that until I got my 870 super mag., after seeing the results with different shells and chokes I'm glad I took the time to do it.