Medium-weight capilene underwear is great to keep you dry. If you have polypro slacks, wear them. Some people inevitably wear hiking boots for the first two trips, though they aren't ideal. For many trips in our region, knee pads are pretty well essential. I can't imagine doing the Tradesman's Entrance, or Tooth Decave, or some of the more challenging long trips, without them.
Elbow pads are pretty nice, but less essential.
A Petzl Zoom can be bought in a number of stores, and is a good purchase. Cheap headlights usually give out after one or two trips. Food and Drink Take along some food and drink. A typical cave day involves three hours in the truck, three hours trekking up and down a mountain, four hours underground, and an hour lying around recovering. Chocolate, sandwiches and Gatorade are the usual fare.