General rule of thumb with handgun rounds is to stay with .40 or bigger caliber.
I own a .45 ACP and .40 S&W handgun for self defense purposes. I practice like a lot with them too so I know how to my weapons like they are my own hand. I need to get some night sights on the .45 ACP handgun.
So many guns and accessories, so few dollars :-)
But not for a newbie, where the "screw up factor" is too high a price to pay. "Did I chamber a round three months ago?" or "does the safety go up or down?" are not questions you want to be asking at 0300 under hyper stress when someone is smashing your door. A revolver takes away all of these pitfalls. Point and shoot.