Just bought ATV and it is stock. Any suggestion's on must have accessories and what not to bother with ?

I don't know what your terrain is like,but I am often in muskeg ,mudholes or rocky terrain,so the first things that I add are more aggressive six ply tires,and a winch.Since I often ride in cold weather,I find heated handgripsa nice option.

The winch is a must, just in case and a good set of more aggressive tire is nice, just as previously mentioned...

My vote is a winch and a good set of gun/bow racks. Make sure the gun/bow racks are the kind with fins. They are a bit more expensive, but are worth it. I can also carry rods and reels/shovels/ and other assorted things like that. I picked up a soft sided cooler from a farm store for $25. I used it more for a soft sided storage bag than anything else. But its nice for trail rides because I can put some ice and carry drinks. I would hold off on the bigger more agggressive tires until you decide you actually need them. They are expensive and although nice to have, not always actually needed. My honda rancher 4x4 has stock tiress and will take me through crap that it shouldn't....

A good winch and some tow straps.The 50' of cable sometimes comes up short. I put a Kolpin Gun Boot on mine.You might consider a treestand carrier.Mine is a U-totem.I've always used stock tires and never had a problem.Walmart has a Rubbermaid tool box.It might be to big for your rear rack. It fit my Honda's well.That was 45.00 compared to a hundred dollars plus ATV ones.I agree the FinnGrips gun holders are a good choice.I'm sure as you use your 4 wheeler you'll see what you could use.On my old Polaris I had ammo cans on the front rack.They came in handy carrying odds and ends.It just came to mind.Buy one of the tire plug kits and a small foot pump.Thankfully never needing it,it's there for an emergency.

Ruger Redhawk

I think a winch and new wheels are good to get too. I'd also recommend getting an ATV bag for your back rack. They are very handy.

Get some new tires and wheels. ITP has some nice wheels and some aggressive tires for off roading.

You don't say the area you are going to be riding in but here is what I must have to travel the forest service roads around my house.
Since I can be a long way from nowhere I have the following.
Check the tool kit that comes with the beast make sure it is complete.
I have a Honda Foreman 450 which has a nice compartment in the back that holds the following nicely.
I large can fix a flat even though my tires are slimmed. 1 quart of oil.( Don't know about the rest of the ATV's if the honda gets low on this it will not run as a saftey feature)
I also tape an extra key to the frame with electrical tape. 50' of good rope along with a decent rachet type of strap that in a pinch you can use to winch if you have to ( Roll over) andDuct tapeall fit in the rear compartment.
Bungee cords strapped to the rack.
And always a full tank of fuel.
I did buy some Gater tires, a winch with plow. I did have some bags on the back but now just bungee a back pack that holds all my hunting needs.
A good double gun/bow finnedrack I also have installed. I also put on some super bright lights as the ones that came with it are a little weak.
Thats my set up anyway and has worked for me.
There is a lot of junk out there that you can put on these things but I just stuck with the stuff I thoughtnecessary and has worked for me for years

I also will be adding some nice bright lights to the front of my Bruin. I want something that will mount tucked in under the front rack, out of harms way. But before I add the accessory lights I will check to see what other higher wattage bulbs are available for the factory light housings because Iwould like to retain a hi/lo option. Maybe there is a bulb available with only a higher wattage on the hi end, that would be swell.

But, for sure, I'm installing a wide beam flood lamp for the rear. I will hook a relay into thereverse indicator light, to put battery power to the light when reverse is engaged. It should be great forin the woods and fields at night, but also for the snowplowing.