Find a range you like.
Take the NRA Basic Pistol Shooting Course.
The instructor may have a variety of pistols in a variety of calibers that you can shoot. He may not. If he doesn't, spend some time at the range renting a variety of pistols. Find what is comfortable
for you.
Price ammunition. You'll find 9mm is about a third less than .40. It adds up.
Backups? Having identical guns isn't really needed. Instead of 3 of the same gun, I'd rather have.....
-.22 pistol, like a Ruger Mark III. Cheap ammo allows for plenty of range time.
-something small for concealed carry in whatever caliber you find you like.
-something in a larger frame, probably in the same caliber as your carry gun, for around the house.
That's not carved in stone, just a thought.
It's important to be a responsible gun owner. This means a gun safe, or at least gun locks.
Also,
listen to Clint Smith.