You sound like a perfect candidate for a Glock 19. If you can have only one, it should be simple, reliable, versatile, and purposeful. The Glock 19 is a great first gun that fits all of these categories. You'll be able to afford shooting it, it's big enough to have fun shooting and small enough to carry, you can find a stupidly large amount of aftermarket accessories out there for it... I could really go on and on. For a one and done handgun purchase, I really can't see you doing much better.
"Intelligence is nothing more than discussing things with others. Limitless wisdom comes of this." - 山本 常朝