I don't intentionally try to limit my calibers, but if I have a choice, I will pick the more common, older, more widely available choice.
Example: A few years back I was looking for a long range target rifle. There are plenty of exotic calibers for that, but I narrowed my choices down to .308Win and 6.5Creedmore. I chose .308. Arguably, you can reach out farther with 6.5, and it is more "in" than .308 these days - but .308 is good to a bit over 1000 yards with the 175gr bullets. The longest range I have access to is 1000 yards. Anything above that, where would I shoot it anyway? I reload, but if I had to buy ammo off the shelf, .308 is cheaper than 6.5, and you find a wider variety (although Gold Medal Match is the only thing I purchase for that .308 - no need to venture beyond that for commercial .308 ammo IMHO). At least the cost difference between .308 and 6.5 was true a few years ago when I bought the .308.
As far as long term stockpiles, I buy tons of 9mm and .223. Those are not worth reloading because they are so cheap. .22LR I have two types - high quality target ammo (most of what I shoot), plus lots of bulk stuff for SHTF - 10's of thousands of rounds. The bulk stuff is mostly CCI MiniMags, Aguila Super Extra and Blazer - I don't mess with junk like ThunderDuds, BucketOfBullets, etc - it's just not worth it, no matter how cheap it is. Other centerfire calibers, both handgun and rifle, I stockpile components for - brass, primers, bullets, powder. I have dies and equipment to reload just about every caliber I shoot. If I need it, I can make it. I buy powders specifically for the target rounds I reload, but for everything else I choose more generic powders that will work across a wide range of calibers - W231, Bullseye, TiteGroup, Unique, TrailDust, etc. You get more rounds for your money buying components rather than finished ammo. I also buy lots of cans of things like 7.62x39, 7.62x54R and 8mm Mauser because those are sealed and will last dang near indefinitely. Cans of 8mm are getting harder to find these days though. But I like that Mauser the best of my "old military" rifles. Well, actually it's tied with the .30 Carbine, which is a real hoot to shoot.