To address the OP's original question, it will depend on several factors. Basics are what calibers do you have or will have, the purpose or at least the possible purposes of your arms. Then prioritize what's most important and needing to stock first, what your low on, what deals aren't worth passing up at least on your primary calibers. A final number is not the most relevant, don't shoot all or most of your stock and build it up.
To buy up to something comfortable, think in cases (usual case size will depend on caliber, 22lr in 5K, shotgun in 250rd, 9, 45, 5.56, etc. usually in 1K, surplus in random sizes). Factory new ball ammo is the cheapest, very realiable and should make anything you own work. Some JHP's aren't so reliable in some guns, let alone being much more expensive to buy in sufficent quantity. But if you can, and you know they work then by all means. There are good deals on very good JHP's out there, even if they aren't the latest and greatest, their still better than FMJ.
The ammo market seems somewhat stable right now, but anyone paying attention to recent and not so recent events knows that the OP's question is a valid one. It's easier and convenient to stock up now, who believes it will stay this way, at least for very long. Last thought is storage.