Unless it's a very a lightweight pistol I don't think dress belts are adequate. A lot of them are just two thin strips of leather with a strip of cardboard in between.
A real gun belt should be at least a quarter in thick, and as tall as your belt loops and holster will accept.
I think it's kind of the same thing with holsters. If you're going to carry anything it should be in a durable, fitted holster with good retention, and not some universal nylon sleeve thing from wal-mart.
Then again, I mostly just carry for bear and bear guns tend to be heavy.