You posted your question in the discussion area for semi-automatic pistols, and the .357 round is for a revolver so I'll just skip right over that.
Being old-school, I always default to suggesting a 1911. There are several brands available that can be found for under $500 street price. Rock Island Armory offers at least one model in 9mm.
However, if this is going to be your one and only pistol and you don't have an inclination to get more deeply involved with tinkering and the mechanics of what makes your gun go "Bang," then I guess I would have to suggest you look at some of the newer designs. Although I personally detest them and will never own one, a Glock would serve your needs and be within your price range. You could also look at Bersa.
There are probably others that would be under $500, but I'm not familiar with the non-1911 market. What I will offer, though, is to be very careful if/when people suggest some of the small, polymer-framed pistols. They're fine for carry and self-defense use, but if the agenda includes using the same pistol for enjoyable range time and/or moderately extensive practice -- the small, lightweight pistols are NOT enjoyable to shoot.