Personally, I think "rigma" sounds horrible. "Gildar" sounds ok but sounds more like a name more than anything..Gildar the Great! I agree with some of the other posters...Gold or Silver sounds just fine.
Ya see, rigmar is a kind of name that, upon immediate observance, sounds horrible and grotesquely abstract. However over time it grows on you. To the point that, I have gone from puking over the name Rigmar to actually becoming rather fond of it. Its more artistic, and has a sense of individuality ... but perhaps it could break the immersion for some people.
As I have stated previously, Florins is my personal favorite. The only downside is that not only is it the modern day currency of Hungary, but it was also used in Medieval2:Total War.
Gold, Reini, Aurum, and Shardii are all appropriate alternatives.