I think you can build a few tiers of water filtration with minimal materials and a bit of elbow grease. Boil afterwards to kill all the tinier nasties and I think you have cleaner drinking water than they seem to have here.
Shamelessly mooching off of Fallout 3: A good investment would be some sort of "EN Survival Guide." type book. Something that has instructions on what to do with your average chakra beasts, what plants/fungus are and aren't safe to eat, a smattering of medical knowledge and first aid, how to filter water, set up basic defenses for a village, etc.
We can toss money at the Nara to get it printed en masse.