OK, first things first. Are you looking for a metallic gold or a NNM gold?
I'm guessing metallic. So yeah, as suggested above, it's easier to do it over a dark base. Personally, I don't dry brush much, but that'll work fine if that's your thing.
1. I'd go with a dark brown base coat by preference something that's not too red and not too grey (Gorthor maybe). Painting gold right over black primer isn't the end of the world, but it's not as easy to make look like you want.
2. Roll a darker gold colour over that (like Bathasar Gold, or maybe Griffon is you want it lighter)) as the base cost. It's best to do this in several thinner coats, especially for larger flat areas like you'll see on bigger vehicles - you get a cleaner, smoother finish.
3. Hit that base coat with a medium to dark brown wash depending on how dark you want the finished product. Again, you might be better served to do two washes rather than one thicker one. A second wash can just over the areas you want to be darker if you're feeling fancy.
4. Go back in with the base gold colour you used. Start brushing in on in thin coats from the areas of greatest highlight down toward the areas of shadow. Maybe check out some basic layering tutorials first if that isn't your thing, you'll see what I mean. Multiple coats may be necessary, but keep 'em thin. Or drybrush, that works just fine too.
5. Depending on how shiny you want you gold, you now have to decide how bright to go. One step, say from Bathasar to Griffon, or from Griffon to Liberator, will give you some depth. For best results I'd go with that highlighting step, and then something even brighter, Liberator (possibly with some bright silver mixed in), to do some final lining around the edges of the brightest highlights.
My apologies if that's more tutorial than you were looking for.
