MD1886 has the answer right: it's more about the location, than the machine settings.
I have to chuckle when I read a newbie lament they wish they could find some gold jewelry. Then someone else comes on and tells them to open up their disc. wide open (rejecting only iron, but digging all else) and "Dig Dig Dig". So the poor newbie goes out to the nearest junky urban blighted park, and digs 1000 aluminum objects, for each or any gold item. Doh!
Thus, the mantra "dig all foil and tabs" and "dig dig dig" is only a very small part of the formula. I mean c'mon guys, it's already a "given" that you can't high disc, and expect to find small gold rings
The bigger picture to upping ones gold jewelry ratio, is to go to where gold jewelry ratios are higher (per the junk ratio) TO BEGIN WITH! And those areas are NOT going to be junky urban turf that is filled with foil wads, can shrapnel, tabs, etc...
The best areas to find gold jewelry, is swimming beaches. Either inland fresh water, or ocean beaches. Beaches are the easiest areas to dig in, and are most conducive to jewelry losses, to begin with. Ie.: slippery suntan lotion, cool waters which shrink fingers, people lying prone on beach blankets to suntan (un-natural prone/flat positions), people frolicking around throwing frisbees and such. And my favorite: people taking off their rings and jewelry for "safekeeping" before entering the water, so they hide it in their shoe, or rolled up in a towel, or other such "safe places".
And if you live near an ocean beach, the best of the best, is when mother nature's storms erode the beach, leaving only the heavier items in a sluice-box riffle-board type fashion (read: goodbye lightweight stuff). Only coins, sinkers, keys, jewelry, etc... Believe me, you're holding your breath when you get foil signals on erosion beach conditions like that. Contrast to a "foil signal" in a junky blighted urban park, guess what it's going to be?