Let's focus on some realsies real quick. Base on the following assumptions: OP is a newbie and not going to spend months in tacticool firearms classes to become John Wick. A self-defense scenario is going to involve a range of 10 feet or less. OP is going to get a concealed carry permit, because the gun sitting on a shelf back home is not helping anyone.
Those statements in place, I recommend a snubby .357 revolver. Here is why. When you're being culturally enriched by diversity, you want a minimum of fiddly controls in the way like safeties or racking the slide to potentially fuck up. And if you have an automatic without a safety and you're carrying it cocked, someone has an unfortunate liability to shoot themselves in the dick when they're trying to draw, which is also not great. A revolver has a long heavy trigger pull, so it's difficult to squeeze hard enough for it to go off while you're drawing it. A revolver has only the bang switch, so there's nothing for even a frightened person to fuck up. Pull it out, point it at the diverse person's belly, pull the trigger until the bangs stop. Five or six .357s in someone's torso will likely handle any scenario with no requirement for aim as they're probably only a few feet away when you're shooting them. Running around with 15+ capacity mags is beyond overkill; if you need that many bullets you're probably already fucked. A revolver's limited capacity is ample enough if you're dealing with a couple people, and even if you're looking at a few people, if you put a couple bullets in one of them the others are likely to not hang around.