My vote is for a 9mm if you want centerfire. Ammo is inexpensive and usually very easy to find. Look at Beretta 92, CZ-75 and especially a Browning High Power. If you will go to a .22lr your ammo is eaven easier to find and less expensive. Check out the Buck Mark and Ruger Mark III. Small grip you may want to look at the Beretta NEOS, its very under rated and a terific gun.
If you like the revolvers buy a .357 because you always have the option of shooting .38. Ammo is a little more costly but you do get 2 guns in one. Light shooter and a heavy stopper.
DONT make the mistake of buying light guns. More recoil and harder to shoot accurate until you get more experience. Think longer barrels like 4"ish.
Have Fun, shoot safe
Concentrated power is not rendered harmless by the good intentions of those who create it.