AR10, ACOG or something else?

[nothinghere2c]

ACOG is the way to go for any battle rifle. They are expensive for sure, but totally worth it.

[l8apex]

Variable optic 1-6, or 2.5-10. Reticle will be dependent on what you plan to use the rifle for. Quality of the optic will depend on what your budget is.

[R19]

Nutnfancy has several videos on optics for AR's. You have to define a Philosophy of Use (POU) first. Yes, please use yards or meters - at first I thought 1,000 yards.

For up to 333 yards, you should start by looking at a red dot sight, 1x4 scope, or a 1xX scope like 6.

[sjb269]

Your an admitted noob and that's cool. We were all noobs at one time! We are here to help.
I know you have probably heard it before…but here it goes anyway, buy a case of 1000 rounds, run irons for a while. Get to the point where you can hit a dinner plate sized target out to 300yds from a supported position and hit a dinner plate size target at 100yards from standing. Then look into a magnified optic.
I have no idea what type of shooting you intend to do with this rifle, however, if you are trying to put a "Battle rifle" together...without training, tactics, and a unit to support you with suppressive/covering fire, a magnified optic isn't going to help you much if the SHTF. It will allow you to have fun punching paper though.
Your magnification needs depend on how tight you want your groups, Accuracy potential of the rifle, if match ammo will be used or not and your shooting ability.
For steel banging out to 300, I would look into something with 6x. Out to 300 a BDC might help. But I don't like them past 300 yds.