There is not really a beginner handguns, if you make a mistake, they all can be lethal, and there is no rewind button if something happen, most news about guns are about tragedies, so first study the subject, hang around the forum and read the posts for awhile, after a couple of weeks you'll be able to separate the chaff from the grain. Ask questions like today.
Then set aside a budget for your first pistol, choose a caliber which is affordable because you'll have to practice, a lot. .22 is the cheapest but its efficiency is marginal at best for self defense, if your purpose is target competition only a .22 is OK because the small recoil. .32, .38 calibers are hard to find sometimes as they are not that popular, if there is a walmart close to your home you'll always find 9mm, and .40 s&w , .45acp is hard to find sometimes.
Mind you all this calibers are for semi autos.
If you choose to get a revolver .38 special is as popular as the 9.mm, in fact the difference is the .38 has a longer shell.
Most guys here seem to prefer .357 special or 44 magnum, but most of us have been shooting for awhile
In my opinion a 9mm caliber is the most popular, if you will use your pistol for personal defense or is going to be your only gun, 9mm is a good start, some guys might have a different opinion and that is good , so pay attention and evaluate.
If eventually you consider on getting a conceal carry license, remember it isn't a license to kill, and if you don't know what you're doing at this point will jeopardize your life, that of your family and everyone around, so be prepared to learn from real instructors, pay one if you can afford one, it costs about $40.00 per hour at any range.