Quoted:
Besides mags and ammo, a sling, light and optic. The rest can wait until you've used it a bit. It's definitely fun to bolt on 20 pounds of crap onto your rifle. But after humping it a while or using it, your rifle will shed weight realllllllly fast.
This..
Sling for functional carrying, upgrade number of mags/ ammo, and purchase some decent targets if your ranges are anything like what I have up here in ND.. Set up your own, open to the public, we have rows of earth and tires covered in rubber to hold the targets you bring. That said.. 10-12" gong steel targets are very fun after everything's broken in and zeroed.
Only thing that I changed on my rifle within the first 1000 rounds was added a new end plate to the upper receiver for the attachment of a 1 point sling.