I've been doing my own oil changes on my '03 Corolla LE, and keep a couple of new gaskets up my sleeve in case I need one. So far, I've been able to simply clean up the old gasket and re-install it without any leaks. I find it has more of a tendency to stick to the plug itself than the oil pan; if it didn't come off with the plug, it would most likely pop off and into whatevr container you are draining your oil -- necessitating a messy recovery job if you don't have a replacement gasket immediately to hand.
I would not want to install the drain plug without a gasket, since this may encourage one to over-tighten it. The gasket is there because it serves a useful function -- don't second-guess it. They are cheap as chips and readily available at your Toyota Dealer's Parts Department.