No "disclaimers" in my post, ok? I'll use common, everyday, factual terminology (which sometimes offends the faint of heart).

A handgun for self-defense is meant to kill. It is a deadly weapon. It's not to wound or "incapacitate". At the moment the decision is made to use it, the victim's life is in danger and the attacker cannot be stopped any other way. Death is imminent - for one or the other. Make sure it's the other.

I'd recommend a .40 caliber semi-auto from a reputable manufacturer. SIG Arms, Heckler & Koch, and Glock come immediately to mind. There are others, of course. Get three magazines (or more). Get a double-action only, meaning it fires like a revolver - each pull of the trigger fires and resets the hammer.

Other accessories (some of which you probably already own): hearing protection; magazine reloading assist; carry bag for going to the range; gun cleaning kit for .40 cal (or any with extra .40 cal brushes); holster (Isreali Fobus friction-retention paddle holster is one of my favorites [NO retention strap or release button!]).

Learn how to shoot it well from your brother or other instructor(s) and practice often. Make sure you learn, understand, and practice (to the point of muscle memory) the "tap, rack, bang" principle for the inevitable misfeed. Generally speaking, the better quality the weapon and the better care given to it, the lesser the chance of misfeeds and other problems.

Good luck! By using your 2nd Amendment rights and enhancing them by getting a "self-defense" weapon, you are, in my oh-so-humble opinion, a great American!