Image source: http://www.geocities.ws/fletcher1/BatteryTrom-2.jpg
The two most common pieces of equipment in gold prospecting are the gold pan, and the sluice box. Gold pans are cheap, anywhere from 5-15 dollars. Black plastic is what I prefer. The gold shows up perfectly against the black. Sluice boxes, on the other hand, can get a bit pricey. Building a sluice is actually a lot simpler than it sounds. Using pieces of plastic cut into simple geometric shapes (squares and rectangles) we build a very lightweight sluice box from plastic simply by gluing the pieces together with plastic cement and waiting 24 hours. For plans on building your own sluice box, one simply has to type in "sluice box plans" into google and they'll find dozens of step by step instructions on how to build their very own gold catching contraption. A sluice box is simple, it's a box, for crying out loud. Who can't build a box? Some outfitters try and sell you on lightweight airplane aluminum and other nonsense, charging hundreds of dollars for a sluice box, but why pay the money when you can literally build most of the gold prospecting equipment you'll need for a matter of a few dollars in materials.
But back to the sluice box for a moment. Lightweight plastic is easy to work with. As long as one doesn't buy sheets more than a quarter inch thick, it can be reasonably cut with an exacto blade. Add to that the cost of a bottle of plastic cement and you'll have your very own sluice box in a matter of a few hours and whatever other pieces of gold prospecting equipment you'll need.
The only thing left to do is find a river that has a reasonable amount of gold still hiding away. In California, that's pretty easy to do. Rivers with gold are peppered throughout northern and southern California. Other places might have less abundance, but hopefully if you're reading this, it's because you already know of a place you want to check out.