Guns in general are very reliable, so a backup is not likely needed. Buy ammo.
I'm not sure what you mean by supplies. A carry gun should be minimally lubricated, my manual calls it "dry" lubricated after being lubed and wiped dry to prevent dirt lint accumulation.
Wet lube before going to the range. My tube of high pressure grease is prolly thirty years old. I use a bore-snake, toothbrush, and occasionally ram a nylon patch wetted with Hoppes #9.