The less-than-pure 14K gold is often created by taking pure gold (24K) and alloying it with silver and copper to give it the hardness or lustre that the maker wants. But combinations of gold, silver and copper aren't magnetic.
Testing gold with a magnet will tell if iron or other ferromagnetic material is alloyed with the gold, but if the magnet does not pick up the gold item being tested, we know nothing more about that gold.
Some gold is alloyed with nickel, and nickel is magnetic. A gold and nickel alloy will respond to a magnet. But what can be told from this? Only that the magnet is reacting to a ferromagnetic material. And that is all.
Gold and silver are not magnetic metals, so these metals are not attracted to a magnet, the only substances that stick to magnets are iron, cobalt and nickle.