Toby1858, a lot of people come on forums saying the trick to finding gold jewelry, is to lower the disc. and dig tabs, foil, and aluminum till your arms fall off. That is not entirely true. A MAJOR factor in getting more gold, verses junk, is WHERE you are hunting. Not simply lowering your disc, and going into junky blighted parks.
For example: some friends and I had the unique opportunity to hit a scraped old-town park in San Francisco, that was being scraped to make way for artifical turf. As time went on, the old soil (from deeper levels) was mixed in with shallower soil/grass, so there came a point, where we could no longer make guesses on shallow verses deep, since all the targets (old verses new) were getting jumbled together. So since it was a demolition site (easy to dig), we had a "relic hunt" mindset. Ie.: no discrimination except iron only, so as "not to miss anything".
Now mind you, this park was one of those blighted inner city parks, where no one had ever seriously detected it, d/t the abundance of surface wino screw caps, foil, zinc, etc... So when everything started getting scraped and re-packed, moved around, etc... it was a gold mine of both old silver coins, mixed together with annoying modern junk. But we meticulously worked all conductive targets out, in our quest for the old coins. The reason I recount this, is it shed good light on the "ratios" you are seeking to discover. We kept all our junk, coins, etc... each night, and made charts for use in a later article we intended to write about the experience. We found that for every gold piece of jewelry found, there was inevitably 200 pieces or more of aluminum junk that had to be dug. In other words, it simply would not have been worth it, to strip-mine a junky park like that, for gold jewelry. A person would simply go nuts, or get kicked out of the park d/t too many holes. But since we hit it during construction, we could dig at will easily, in loose dirt. It was a real eye-opener.
Now I grant you, there are certain caliber neighborhoods, or turf-type usages, where the wino screw caps won't be as abundant, and jewelry losses may increase. But it still told me that for someone looking to up their jewelry ratios, their time would be MUCH BETTER spent ....... not simply worrying about turning down the disc, but to ALSO simply find a better hunt site.
The "better hunt site" for gold jewelry, is swimming beaches, pure and simple. Either fresh water lakes, ocean, etc... This is because the very nature of swimming beaches is much more condusive to jewelry losses to begin with: People lathering up with slippery suntan lotion, entering cooler waters which shrink fingers. People swimming vertically, or lying vertically on beach blankets (an unatural position) thus increasing odds of things like necklaces and bracelets to come off. People pitching frisbees and footballs back and forth, or frolicking their arms in volleyball, etc.... Or the one I like best: people taking off their jewelry "for safe-keeping" before they enter the water. Yup, you guessed it: they put it in their shoe for hiding, etc... And even if the water is too cold for swimming, and you're only talking about wading: What's the natural human instinct to do when you enter the water up to your knees or waist? You start fanning and splashing the water around with your hands, right? All of this is recipes for jewelry losses.
And on the beach, there's no lawn-mowers to make can slaw. And the beach is much easier to dig in.
Of course, even beaches can vary beach by beach. If you end up at a party beach, where thousands of teenagers drink beer at frat parties, and burn pallet bonfires, well then of course the tab and molten can nuggets (molten aluminum globs created when people throw aluminum cans into bonfires) will be punishing.
And if you are lucky enough to be near the ocean beach when mother nature sends a good swell and high tide to work together to erode the beach, you can actually end up on eroded beach sections where the answer to your question would be "absolutely no aluminum at all, for each gold item" (or heavy item of any sort). Because mother nature takes all the light stuff out to the ocean, leaving only the heavier coins, lead, brass, copper, gold, silver, etc....
