Any 3" or 3.5" shell in 4 shot, will do just fine.
You will need a turkey choke tube: X-full or XX-full.
Get them to within 40 yards and aim for the head.
More lead in their head = less lead on your table.
Get some calls and practice.
This is where you get to pay your kids back for those violin lessons.
Watch videos. They are the best way to self teach.
They never show you everything, but they leave big hints as to how they got where they did.
They almost never show you how to find their roost. Thats the sneaky, not film worthy, part of the job. And my favorite.
I have two known customers that use a .17HMR to hunt turkey.
They use ballistic tips and shoot for necks. If they miss, they miss clean.
A "hit" at 50 yards means a headless turkey.
Be sure and take your "Orange" with you, and wear it when you move around.
Never be near a decoy without your Orange on.
Never place a decoy, on public land, near you.
Be safe.