It might not sound logical, but gold (here I mean the gradient imitating gold, not yellow), either over white, black or red background would look on the screen rather cheap than noble. If you are not designing a casino or a jeweller store or your intention is not to make something kitschy deliberately – it might be good to leave it.

Cheap things are usually underlined by shouting ads. Yellow-black, red-black, bright yellow-blue combinations, trying to attract viewers’ attention would look cheap.  The same is with clear primary colors yellow, red or blue, on white background. Pink would also probably look cheap, because it is thought to be kitschy, but there are exceptions.

Black things are often expensive. A lot of people, especially designers find black things cool: black cars, black clothing... Black on the screen does not necessarily have this association. Black sites are the domain of hackers, porno-sites, Satanists and other suicidally endangered species. Black background would only do, if combined with colored surfaces, whose brightness would be underlined by black.

Expensive things would rather require more complex or extravagant colors and thus much more color sensitivity and experience.

Another way to make things look valuable is reducing colorfulness and using neutral tones such as cold/warm grey, beige, cream alone or combined with soft tones. 

Photos and motives with reduced saturation, in monochrome color or black and white would rather look more sophisticated, than normal color photos with their common look.

A combination with white can make even the wildest color combinations suitable for “serious” clients and purposes.