Free: Contests & Raffles.
I'm a beginner turkey hunter, but you are asking some basic questions so I'll take a stab.For both ducks and turkey, I haven't seen much, if any, improvement going from factory to expensive choke. Of course that will depend on the gun,load, etc.I would start by buying some quality turkey shells (prepare for sticker shock) and go pattern them. You can print out free 8.5x11 turkey targets which I like because it's easy to see and count the number of pellets in the vitals.From there, go shoot at yardages you are comfortable with. The pattern should be very tight with a nice spread within a small circle. Similar to waterfowl, you want good even coverage within that circle, but a smaller circle than for ducks. If your bead is aiming point of impact and you can effectively hit the target at distances you are happy with, no need to go any further. My thought is that sights are for those that either want them, want to shoot accurately farther, don't have a bead or the bead is off and they can't adjust and don't want to hold off for that.
Throw in the factory full choke and pattern it, may need to try a few different loads and 3 1/2” shells are not necessarily going to pattern better than 3” shells. I’d recommend the Winchester longbeard XR, I think they are the best lead loads out there. You don’t need a scope, limit your shots to 40 yards and shoot them in the neck. Benelli’s typically shoot high so you will want to pay attention where you are holding and where the majority of your pattern is.