Here is a great site I found on choosing a pistol.
If you want my quick and simple weapon recommendation for a handgun of choice I’d go with a Glock 19 for 9mm or a Glock 23 if you want to have a .40 S&W.
These two weapons are built on the same platform and can function as weapons for concealed carry or as a primary service weapon that you might have on your nightstand. So if you intend to go with only one weapon I’d choose one of these two.
9mm will give you more practice time if your funds are scarce while the .40 will offer more stopping power depending on the round used.
One other main benefit of the Glock is the availability of the Advantage Arms .22 adapter that will give you trigger time at 1/3 the cost per round. I’ve found that I need to use CCI mini-mags in this adapter to get reliable function but that still leaves you paying approx. 7 cents per round versus 21 cents per round.