My first year, I picked up a cheap box call, a few mouth calls, a cheap pot and peg call, and a push button call that would clam to my gun barrell. I put it all in a fanny pack and got a seat cushion that I used deer hunting. I (like spatrat) was not going to break the bank on something I didn't know if I'd like or not. Then after the season and bagging my first bird, I hit the clearance asle at Wally World. Now going into my 5th year, I have too much stuff to list and am constantly looking for something else to add. (never replace) You can get by with a little to get you started, but you'll get the bug I'd put money on it. And I've never bet unless it was a sure thing.

Popere, Think I will cause a stir here, forget the 3" shell! Take a AA in 23/4", Win 209 Primer, 34grs. Win 540 powder or HS6, Win F114 wad and 11/4 of #4 or #5 platted shot, PERFECT turkey load. Velocity is right at 1220 ft/sec. Won't leave a bruise either. I can load 25 for $3.75. I am shooting this out of a Win 1300 with a full choke. Not extra or super or turkey full, just full. The best shell I have ever shot and I have shot most of them. I even played with the duplex loads for a while, this is better.
As for a vest I have an old H.S. vest, love it. All my stuff has a pocket inside so it doesn't bang around. Have fun, shoot a lot of paper targets and play with chokes and shells and see what works best with your gun.
Gselkhunter

Remington 870 Super Mag & Remington Super Full Turkey Choke....lethal.

You need to try various combinations of shell and choke, on patterning boards, before going in the woods. Not all shells and all chokes work the best in combination, and what works for my gun might not work the same in yours. Also, polish your barrel. I think there are some old posts on that to review. Adds to pattern effectiveness.

Vest--I'd say buy a SuperElite II if you can afford it, if not, wait a year, put it on your birthday/Christmas gift list, etc., and spend the money this year on shells and patterning your gun/choke combo.