There are 2 primary types of sailing, cruising and racing. Although you can do both with any type of boat, the more masts and sails on a boat, the longer the boat, and the more complex to steer, requiring more crew. And the more tight-knit the crew, the better the experience.
"Boat shoes", which typically have white soles. Also, water shoes, flipflops, or even barefoot.
Change of clothes
The types of boat may require the use of personal flotation devices. PFDs will typically be on-board.