What's your budget? What's budget for one person may be different for another.
I recommend a vertical grip or hand stop for quick, correct hand placement. The magpul vertical grips and larue hand stops are good IMO.
Also a good compensater/muzzle brake on the barrel. I like the VG6 Gamma 5.56, keeps the barrel down for increased accuracy. It barks pretty good though, doesn't hide flash very well, and the gas coming from the sides is no fun for people standing next to you but in a home defense situation quick follow up shots are a must and the Gamma does well to help. I really like it a lot.
For home defense I would do a true 1x red dot but if your hunting you may want magnification. I always have backup irons and an optic with quick detach base in case the optic fails it can be dumped quick for iron use. I like the gen2 magpul irons that flip up, check to make sure they are authentic though. I'm not sure if they have a newer generation or not. Of course if you have a fixed front sight gas block you would either have to switch out the block or just get a rear sight if the rifle doesn't have one already. If you do a true 1x red dot you can cowitness so optic doesn't need taken off for iron use. You can always do a magnified optic on top and a 45 degree red dot but at the cost of added weight. I personally have a separate upper just for hunting use so I don't have more weight than necessary. You could always have both optics on quick detach mounts and switch them on and off for whatever your using it for, just make sure you attach the same way every time to ensure your zero doesn't change much.
Flashlight is a must for home defense. I like the inforce lights personally.
Idk if your a member but ar15.com classifieds is a great place to get quality parts at a good price. Only buy from people with good feedback and check to make sure product is authentic before purchasing. It's not uncommon to find Aimpoints comp m2 for around $150-$200 but like I said check authenticity by serial number and various YouTube videos and threads helping spot fakes. Also don't purchase military models, Aimpoint won't repair.
The accessories like the hand stop, vertical grip, and maybe the flashlight will require a hand guard that's either a mlok, key mod, quad rail, or similar so you can mount them forward of the upper toward the end of the barrel. If you haven't bought the rifle yet I recommend buying one that already has a handguard like I mentioned already on it, that way you don't need to switch any parts out. Free float would be ideal. Building the rifle yourself can not only save money but is fun being able to customize to your liking from scratch rather than taken off parts. You would have to buy a few tools but assembly is pretty straight forward with lots of resources to help.
I would be happy to give more or alter my recommendations based on what you actually want to spend
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