Think of your future gun as a tool - a power tool. You need to know enough about it to select the right one for the job and you need to understand how to use it safely and effectively.
Talking with experienced gun owners will help you clarify your objectives and identify the kinds of guns that will meet your needs.
Find a gun shop and a gun range near you and talk to the people there for starters. They are usually quite knowledgeable and most ranges have guns you can rent or try. You can look at different guns, handle them, price them and get an idea of what appeals to you
If you have a friend or relative familiar with guns talk to them and pick their brains. Most gun owners will be happy to share info and experience with others and even take them along to do some shooting .
As others here have said, for personal defense you can’t go wrong with a .357 revolver (or a .38), and a 12 ga. pump shotgun for home defense to start with. These two weapons are probably the most common combination people start with.
As many people will tell you, a revolver is the simplest, safest, easiest to use and most reliable type of pistol. And the sound of a 12 ga. shotgun being cocked will strike fear in the most determined home invader.
Good luck.
...and give away your position. Besides some of these thugs are so stupid, they wouldn't know what the sound was anyway.