Mincosting golds has about the same priority as with anything else. Soldiers, healers, and heavies take precedence over rogues, bandits, and mages. And so on.

Currently, I have Iris, Julian, Cuterie, and Themis at mincost. Of those, I'd highly suggest mincosting Iris and Julian.

Fedora and Bernice are at -2, but those two definitely benefit from mincost as well.

Yuyu has the same AW passive as Fedora, so likewise, CR her if you can.

Of the ones you listed, Gina is actually a solid gold unit, so combining copies isn't a bad idea.

Otherwise, for unlimited Conrads and Garretts, I tend to use them as pseudo-plat armors.