Race bike minimalist seat bag: 1 tube, 1 plastic tire lever, one tire boot, one CO2 cartridge.
Commuter or travel bike: 1 tube, patch kit, steel tire levers, boots, multi-tool, CO2s. I have a frame pump that I usually carry on long and/or isolated, unfamiliar rides, like the French Pyrenees, or the Canadian Rockies.
I keep a CO2 inflator with a cartridge in my jersey pocket on most rides.
The best tire boots are made by cutting up an old tire into approximately 2" pieces, then cutting the beads off of these chunks. They allow even a badly sliced tire to be ridden indefinitely. I have ridden tires booted this way until the tread wore out.