I believe that you absolutely need a complete buttstock cleaning kit for the rifle. In the true essence of a rifleman, you need to be able to completely dissasemble and clean the rifle when you're out in the field. You don't USE the kit for day-to-day stuff, but if you NEED it, it'll be there for you. A fighting rifle deserves to be prepared correctly. The buttstock cleaning kit comes with a sectional rod, a scredriver tip, a wrench for the gas system, a handle for the cleaning rod, a bore brush, a chamber brush, a vial of grease, and a tool that helps load mags and also dissasemble the bolt.
Cost: $10 from Fred's in NC. Look in a Shotgun News for the ad.
The USGI mags are a given as well, $31 each from Cole's...you won't find them cheaper. Avaiod knock-offs like the plague.
I like the ARMS #18 mount, and the ARMS #22 rings. As a set, they're guaranteed to keep they're zero after removal and attachment as many times as you want. BEEFY, too.