Maybe.
The real issue is twofold. First, how much shooting will you do with the more-expensive-than-range-ammo-self-defense-ammunition? You can't buy 100 rounds and shoot 95 rounds at the range to see if it works in your gun, right? But if you shoot 50 rounds then you've got 50 left and you're good to go for your carry gun or home defense weapon - under normal situations.
And that's whatever platform you're considering, handguns, long guns, whatever your choice is then you need some left over.
That's the casual answer. Simply put, a sufficient amount the day that you need it. And if you're switching off guns and calibers then the number of rounds has to match the guns and calibers.
Simple.
The second issue is different. What are you preparing for? Ignoring "end times" as an unrealistic answer, are you expecting to need ammunition to ward off street rioters at your door? Are you concerned about major civil unrest after November 3rd? Do you expect full bore fire fights in the streets? In the streets where you figure you will be? On your block?
Then the answer is as much ammunition as you can afford. 1000 rounds? 10,000 rounds? How big a battle are you concerned about?
I understand that 200 or so rounds of 5.56 NATO is the usual amount of ammunition for an Army infantryman to carry into the field. If you have 20 round magazines that's ten magazines and plenty of weight. So, if the fecal matter hits the whirling blades and we have a street war going on then I guess you need a couple of hundred rounds on you if you're carrying an AR-type rifle. If that's true, you probably need several thousand rounds hidden at home don't you think?
What if you're going out with a handgun? Let's say a M92 Beretta with a 15 round magazine. Ten of those is 150 rounds available - do you think you're getting into a fire fight with your handgun and you'll need 150 rounds? Okay......worst case fictional scenario, yes. Then I'd figure you need 1000 rounds more hidden at home don't you think?
So, you decide. Do you really expect to get into that big a fight? Are you a prepper with several months of food available? Do you even have two weeks of food available? How much food do you think that you'll need? You. Your family. Your pets. How much?
If you can make that determination then match it with ammunition if you're concerned about civil unrest or riots.
If it's just daily carry and a home defense weapon, well, that's a
whole nuthuh smoke, podnuh, and go back to where I started.
Oh, and BTW, since all you're talking about is 9mm and .380 ACP, a couple of hundred rounds for each is a minimum all the time. Range ammo will carry the day if the rioters hit; they don't care what you're loading in your weapons and neither should you.