Heck, I got guns and ammo that would be used to trade for necessary items. I figure a good rifle and and a couple hundred rounds would be worth it's weight in gold (or something more practical in a survival situation) to someone who does not have a weapon. Plus it could help arm any group I might connect with.
I don't use one type of ammo for any particular caliber/gun, and instead keep a wide range for any contingency. For example, with 12-gauge I've got 20 rounds rifled slugs, 100 rounds "00" buck, 100 rounds #4, 200 rounds #6, and 200 rounds #8. Like others have said you can never have too much, and for 12-gauge I only have about half of what I'd like, although all my other ammo is pretty much stocked to my liking. I don't worry about having too much, because if the SHTF I can always barter my ammo for some goods as others have also mentioned.
2000rnds 9mm about 1500 quality fmj rounds 500 quality jhp
1000rnds of .38spl preferably a good Lswc
500rnds of .357 same good Lswc bullet
500rnds of .44mag
500rnds various 12 gauge loads
1000rnds 7.62x39 fmj
I have 2 high powered rifles and I think 100rnds for each would be sufficient as I'm not planning on trying to reach out and touch somebody my eyes ain't that good.