I think gold has numerous meanings, but in order to get them all, we have to look at it from both the original pagan ideas that prompted the telling of the story, as well as the Christianity that was added to it when it was written down.
Gold for the original Scandinavians (prior to Christianity) was not just a symbol of wealth - it also seemed to represent light and goodness. I don't mean "goodness" the way we think of it in terms of the Judeo-Christian influence. I mean that gold not only looked like beauty and light - it was light for a civilization that spent a large amount of their time stuck in the darkness and cold of winter - a symbol of the sun and the coming of warmth again. Gold also represented generosity - the good men were the ring-givers, the givers of this beautiful stuff, not the evil, twisted men (and dragons) who hoarded it all to themselves.
Once Christianity got written into the story, I think the gold still represented light and beauty, but the goodness it represented became that of God giving the gift of His Son, Christ, to the world. Men who gave away their gold were "richer" and more noble than those who greedily hoarded it (especially if they gave to the Church, of course)! :)
As I am currently pretty much snowed in at my house, and summer seems like an awfully long time away, that could be coloring my take on this a bit. So, of course, grab yourself a grain of salt! :)