Dick,
Are you refining karat gold? Most contaminants come from poor rinsing, if you use a small aspirator, a small buchner funnel, and a vacuum flask you can filter your precipitated sponge and rinse it well. You shouldn't have to drop twice.
A few tricks, if you inquart or not, dilute your aqua regia with cold water and add ice to it. The solubility of silver chloride drops way off with temperature. Cold is good. Then filter it while it is cold. This will remove the biggest contaminant, silver.
You can get an aspirator from Shor International (hope I don't get struck by lightening for saying that!) for 10 bucks.
Oxalic acid does drop gold of high purity but it is expensive, has to be used boiling hot, and it won't solve your issues if your filtration is inadequate. If you inquart, nitric dissolve, digest in AR, chill and filter well, and drop with SMB, and filter and rinse well again, your gold will be better.
If you do this and your gold still is impure, I'll go through it with you step by excruciating step until we find the issue.