A good spare and the means to change it is #1. A small compressor, and valve stem tool will make it easy to air down once you get offroad, because you'll have the ability to air back up when you get back to pavement.
I've plugged tires out in the boonies... you can do it if motivated
I carry a plug kit and patches, and a way to get a tire off rim if necessary.
But a sidewall cut is a little harder, but still having a few supplies and knowing how to do it could save your bacon one day.
Don't be limited in thinking that because your tire store won't patch even the smallest puncture in the center third of the tred, that you can't do a trail patch to get you out of the rough and to a tire store.
For re-seating he beabs to inflated, you wrap a ratchet starp around the circumferance, in the center of the tread area, and crank it down.