Please, do not use PVC for any storage. It outgasses a dilute hydrochloric acid. Look for surplus sonobouy storage tubes, which are made of polyethylene, and already have a nice screw-cap on one end, which can be sealed with silicone sealant. Only bury some cheap SKS and ammo, to be used as a last last-ditch defense. Someone may find it before you do.
Optics: make sure you have a pair of cheap chicom compact binoculars ($20 or less) for each member of your party. You want as many augmented eyes working for you as possible. A spotting scope is also useful to see them before they see you. Make sure you're working from a covered, shaded position. You're looking for glint from the other guy's optics. He may have a sniper looking for some careless reflection off your optics.
Knives: everyday tools that nobody should ever be without. Everybody who doesn't go through metal detectors should carry a decent pocket knife every day. It's one of those tools that you may never need, but if you do, if you don't have your own, nobody else will, either. Also consider a decent sheath knife for every defensive weapon deployed.
Sales: Keep an eye out for the magic word SALE or CLOSEOUT. You may find some great deals out there to upgrade your present equipment at the least likely moment. Keep your older gear. In a crisis, you may be able to turn a trustworthy-but-unprepared neighbor into a valued backup, once you instill some rudimentary skills into him to offset his neglected education.