Use the fattest tires possible. In turns, instead of leaning the bike into the turn, lean your head and upper body as much as possible to provide the counterbalance, as you’d do on a trike, and keep the bike as near vertical as possible. Avoid pebbles like the plague. If it looks like you are going to be forced to turn on gravel, you may safely assume you are going to fall. Brake hard and dramatically reduce your speed to a crawl before you reach the gravel patch. This is your only hope for avoiding a fall, but even then….
For protection, since frequent riders may find a gravel skid nearly inevitable, wear body armor such as that used by mountain bikers. A friend of mine (Neile, Ti-Aero rider and a New York Cycle Club ride leader) wears Six-Six-One armored shorts and roller blade-style elbow pads. I now own some too. Why not. I’d consider some mountain bike body armor with shoulder pads, too.
Lots of MTB armor here, but I don’t know much about the shop.
If and when you lose skin from a skidding fall, take the injury seriously. There is no such thing as “mere road rash.” Anytime you lose skin — one of your body’s main defenses against infection — and dirt (pebbles, gravel, etc.) gets into the wound, you are at substantial risk of infection, which, if inadequately treated, can lead to death. No joke. Immediately scrub the entire road rash wound thoroughly with a medical sponge (or clean gauze pads) and soapy water. The scrubbing will hurt, but you must clean out every speck of dirt, leaving a clean wound that can heal properly. Dress the wound with clean bandages to prevent further infection. If the wound is large, immediately see a doctor. If you’re treating someone else, isolate yourself from their bodily substances (like blood) before touching them.
Those are the basics, but they are not the whole story. You must get training before you give first aid. I strongly recommend taking one of the Wilderness First Aid or Wilderness First Responder courses offered by SOLO before another day goes by.