M1A Scout with Aimpoint Micro optic
AR-15 from Colt, Bravo Company, or Daniel Defense with your choice of optic.
FN SCAR 17 with your choice of optic
AR in 7.62x51mm by Knights Armament, Noveske, or LaRue
FALs...maybe. 18" barrel, top rail, fix the handguards to handle the heat, fix the trigger, ambi safety, change the grip. It needs many modifications while the others are good to go out of the box.
Garand...no. It's fun to have, but stay with a magazine fed weapon for obvious reasons. If the reasons are not obvious, carry on. I'm not going to argue with your choice and would accept your assistance in a situation.
Just remember, the optic makes the gun. Iron sights are fine, but a quality optic will make the gun better. They are worth the price if the reticle meets the criteria for your mission.
If you have NO idea what to get, then just get an AR-15 with a rail on the frame (free floating rail/forearm may give you better accuracy). Add mags, optic, sling and you're done. Example rifles include the Colt 6920 and Bravo Company Mid-Length Mod 0.
If you go with an alternative AR-15 caliber such as 6.8 SPC or 6.5 Grendel, research magazines to determine which brand is most reliable.