I flew over 1,000 hours of cross county flights over about 9 years when I had my business (2004-2013) and on the typical trip I took:
Oil
Funnel
Screwdriver (six-way)
Ties down ropes
One set of mini-chocks
Fuel sump tester
"Fuel Hawk" fuel gage
Plexiglass cleaner and a couple of old t-shirts
Cowl plugs
A roll of paper towels
A handheld comm.
A pulseoximeter
A couple of empty one liter bottles clearly marked "out" with a sharpie. Like this one, with the "flip top" superglued on and the "loopie thing" cut off.
I never carried spare tires, spare mags, spare vacuum pumps, spare alternator belt, etc. I always took the approach of proactively maintaining the bird to minimize the chances of needing a part instead of carrying parts in case something broke. I was stranded with a breakdown exactly once in those 1,000+ hours.
I also don't subscribe to the "dress for egress" philosophy. I simply dress for today's weather. If I'm flying a four hour XC in the summer then you'll find me in Tevas, shorts and a t-shirt. That attitude might change if I was flying out west though. Sure, there are some remote places around here also but how many people "dress for egress" (or worse, for Armageddon) when driving their car? And I guarantee you that in the Ouachitas and Smokies there are plenty of places that, if you ran off the road, they wouldn't find you for days and you'd never climb back up to the road.
I could prepare for WWIII when I fly but, considering the remote possibility of it happening, that's likely not a wise use of my time and resources.
That's just my approach, nothing more nothing less and I'm not dissing anyone who feels otherwise (and that seems to be a necessary disclaimer around here lately).