If you were starting over knowing what you know now, pick these calibers
One each .22, .380, 9mm, .40, 45. And just for fun 1 revolver.
Everything got burnt up in a fire. Insurance covers replacement, so you get a do-over.
.22, Ruger Mark whatever is current, target version.
.380, if I'm going to use it for carry, LCP custom, for the better sights. Not the LCPII. If not for carry, Beretta 85, or CZ83, or something with some historic significance.
9mm, XDS or Glock 26. This and/or the snubby will be the main carry gun(s).
.40, XD subcompact (still). Carry alternative.
.45, pick some decent 1911, tweak as desired. They're just a hoot to shoot. Can be carried in a pinch.
I'd probably have more than "a revolver", but if only one, S&W Performance Center Pro 640. A bit more of a gun than my current 642.