Best advice so far: CLEAN THE GUN BEFORE YOUR FIRST RANGE VISIT. Second: DON"T USE THE CHEAPEST, POS AMMO YOU CAN FIND.
THere's no set method for 'breaking in' the barrel. As far as I know, Uncle Sam doesn't bother with this bit of folklore. With today's metals and manufacturing abilities I consider it a thing of the past. But of course it's your gun, do as you please. If all else fails, RTFM.
Oil? You're going to get A LOT of posts on this because everybody does it different. Probably one consistent point they will make is that ARs like to be wet, not dripping of course, but unlike pistols, everything likes to be coated.
Use a good GUN oil and you should be fine. I think there's more difference in hype than actual contents but again, it's up to you. For God's sake, use GUN oil though.
Me, I'm a Froglube guy for my ARs.