What, you've never heard of Thomas Parke D'Invilliers? That's because Fitzgerald made him up. This is breaking the normal rules of epigraphs, which usually use someone else's words and not the author's. On top of that, this fictional Thomas guy made an appearance in another one of Fitzgerald's novels as a typical college intellectual in This Side of Paradise. So basically, we get an idea of Fitzgerald's trickiness and perhaps literary hubris before the story even begins.
The epigraph seems to be talking about someone using material deception in order to win a girl. In other words, bling yourself out to attract the attention of a woman who wouldn't otherwise notice you. And that's just what Gatsby does.
But notice that it's not just a gold hat—the "lover" of this epigraph is bouncing, too. Okay, now picture a man bouncing up and down while wearing, say, a gold top hat. Did you giggle a little? We're pretty sure this is supposed to be kind of absurd, like Fitzgerald is telling us already that there's no way this situation can possibly end well.
Poor, gold-hatted Gatsby.