Plenty of ammo is a must.
True that is.
OTOH, if you're at the point where you have to use your ammo, you've already failed at not being discovered. Once they've found you, it's only a matter of time -- as they say, you have to sleep eventually.
Seems to me the best prep is to make yourself invisible.
I live out in a very rural area, on the side of a hill where no one except helos and planes can see me, with a half-mile uphill driveway and woods with ravines on all sides. Have my own power, water, and there's critters and deer aplenty. That's nowhere near enough to be totally self-sufficient, of course, but I will say this: other than the driveway, I'm hard to discover, and the driveway can be blocked easily (that's a mixed blessing...)
Saw something new at Bi-Mart today: 2000 rd cases of SS109.