No one right answer.
Again, bug in, more calibers, the more likely you can use any ammo your find later.
Bug out, how many people.
One or two people, 5.56 rifles and 9mm or 45 pistols. Possibly a .22 conversion and some .22 ammo for small game. Or maybe one .22 pistol.
Add more people, especially children, I would add at least a .22 rifle. And if more adults, a .308 rifle. I would probably stick with a single caliber for pistols.
Also, how are you bugging out? On foot? You will be seriously limited to how much ammo you can carry. Think not? Grab a case of 5.56 and carry it a mile. And that is without a rifle or food or anything else.
If in a vehicle, you can carry a lot more. In that case, even with 1 or 2, I would add at least one .22 rifle, one .22 handgun, and a LOT of .22 (you can barter the extra). And definitely a .308 rifle.
In a nutshell, ^^THIS
Whatever one feels comfortable with, can afford, can train with and what 'situation' is being prepared for. SHTF/TEOTWAWKI, may be continue for a long time but many localized situations such as hurricanes/tornadoes, electrical grid, civil unrest likely will not. I'm preparing for the latter not every conceivable exigency