Glock 19 or SigP226 - 9mm platforms, high capacity magazines, ammo is relatively cheap and plentiful. Both are very durable and easy to maintain. Glock is much less expensive.
Take basic gun safety and shooting training courses and practice every time you can. Then, take a course dealing with what happens when you shoot someone and the ethics of self defense. You must be confident you can do it if the time ever comes.
I am always reluctant to recommend Glocks to new gun owners. That safety on the trigger is not much of a safety until you learn to keep your finger off the trigger until ready to fire. I have a G19 and it is very reliable. It is just the light trigger pull and where the safety is located that makes me reluctant to recommend it. A 357 magnum can be loaded with 48 special for lower recoil so that could be an interesting option.
40 posts before the first mention of Glock! We love our glocks. I personally have trouble with any slide on any handgun so for my personal regular use I have a Ruger SP101 revolver, what a beauty she is. I might add, every home should have a shotgun for home defense.