Like Heather, I don't take spare buckles or tent poles, but you have to consider in regards to the trip you're taking and experience with the gear you're bringing.

Two kinds of tape? I seldom ever use the tape I bring.

Three people carrying 50ft of cord each? Not if you all intend on staying together.

Same with a first-aid kit. Take more stuff maybe, but only take one kit.

A radio? I never brought one for years. About 10 years ago a I got a walkie-talkie with a built-in NOAA weather radio and I've brought that on a few trips when I was with a group and could share some other gear. But it was the weather info I wanted, not the walkie-talkie.

Redundancy... a couple spare lighters, some extra LED lighting, an SOL emergency blanket, a couple clif bars, a small knife, reading glasses. Off the top of my head, that's about it.

I would first concentrate on the gear that only you will use, then discuss with the rest of your group what you can share and what of that you will be carrying. If you have some headroom in your pack after all that's loaded, add a few luxuries for yourself and enjoy them while you're out there