You will love the M&P. I did mine, except for the fact that it was chambered in 5.45X39
PITA to find around here after a while. I sold it. I want to get another later that is 5.56.
The .22 conversion is really nice because you can work on trigger discipline without burning up expensive ammo. I'd suggest getting one.
Outside of that, I had a folding vert grip and a good sling with a T dot sight, not a scope. Unless yours has a DM barrel on it, I wouldn't bother with anything over 4X. Have a good bolt action rifle for that.
This is what it looked like except for the grip.
And with the grip. I did have a light on it for a while, but switched it out to my 870.
Right now I have a DPMS Panther lite that is just as plain jane as can be. I even ditched the adjustable stock for a fixed. It weighs like 6lbs with a full mag.
This was before I switched out the stock.