Solubility of gold salt solution?
Old question, but I thought I'd add to it:

In your example, the first undissolved solid is indeed gold. It's not easily dissolved by $\ce{HNO3}$ alone, but requires a mixture of $\ce{HNO3}$ and $\ce{HCl}$ (aqua regia). $\ce{Ag}$ and $\ce{Cu}$ would dissolve by hot $\ce{HNO3}$. The precipitate formed by addition of $\ce{HCl}$ is indeed $\ce{AgCl}$, so you're on the right track.

A brief list from experience:
[At room temperature in aqueous solution]

$\bullet \ce{Au2S}$: insoluble (quite sure this is the precipitate formed in basic solution when sodium metabisulfite is added to $\ce{HAuCl4}$. Either that or $\ce{Au2S3}$).

$\bullet \ce{AuCl3}$: highly soluble (can be formed by dehydrating and evaporating $\ce{HCl}$ from $\ce{HAuCl4}$, which is the product of $\ce{Au}$ dissolved in aqua regia).

$\bullet \ce{KAu(CN)4}$: soluble

$\bullet \ce{KAu(CN)2}$: soluble

$\bullet \ce{AgCl}$: insoluble

$\bullet \ce{CuCl2}$: highly soluble

$\bullet \ce{CuCl}$: soluble, but harder to synthesize than $\ce{CuCl2}$

$\bullet \ce{(Au/Ag/Cu)(NO3)_x}$: soluble ($x = 1,2$)

I think the overall result here is that gold, silver, and copper salts generally follow one of the primary trends of solubility: that is, that $\ce{NO3-}$ salts are always soluble regardless of cation, and $\ce{Cl-}$ are usually soluble except in cases $\ce{Ag+}$, $\ce{Pb^{2+}}$ and $\ce{Hg+}$.