Hayhauler I know you say you wouldn't recognize a gemstone, but once you see some for sure you will. I don't know about all gemstones but some gemstones are heavy and they end up in the 'black sand concentrates' and man are they pretty.They also usually have a higher index of refraction then quartz crystal so they stand out (for example Zircon, Diamond and Topaz.) See here:
http://www.allaboutgemstones.com/gemstone_refractive_index.html
One of the first times I panned a creek I got some little red sparkling garnets and they looked like rubies to me. Another time I was out panning at a local river and I got an oblong black crystal in my pan that turned out to be Schorl (black tourmaline). Since then, I have found garnets aplenty, some ruby spharelite, ruby,topaz, emerald and lots of quartz crystals.
I have specimen stones with all kinds of gemstone inclusions I have picked up in the Mtns here and even some nearby.
So even if you don't find gold right away there's other valuable things that are fun to find out there. Not to mention the other heavy minerals which could also be valuable like silver, galena, chromium, platinum and the rare earths...
A few things to look for in gemstones:
Is it Faceted (how many sides does it have)? What shape does it have (round square etc)? What color (bright gems are usually worth more then cloudy ones etc)? Is it clear (clarity)?, How big?
I'm sure there's more but anytime you find something neat, interesting or shiny/sparkly, keep it, it just might be quite valuable. Good luck and welcome to the hobby!
PS Rock hounders will pay good money for neat specimen stones of gemstones/crystals/pretty minerals so its something to keep an eye out for.