kthonk,
Accuracy is relative to a lot of things, including trigger, barrel, loads, etc. No one here can give you any kind of an idea of what you can expect from your particular rifle.
That said, the typical AR15 with standard military rounds usually will do 3" or less easily at a hundred yards in the hands of a competent rifleman. Some will do better. Note the competent rifleman part.
For loads, I suggest you start at the bullet manufacturer's low recommended in and work yourself up a load. Suggested loads you get on the internet may very likely be above or below the ideal load for your rifle. The only sure and safe way to get a good load for your rifle is to work your way up from the low end of your reloading manual's low suggested end for the powder you have.
Doing this, along with doing solid case prep and having a good trigger job on your rifle will get a good bit of the accuracy out of your rifle. BTW, there's a good treatise on reloading for accuracy in the book Metallic Cartridge Reloading.
Regards,
Dave