A mallet is the only piece of equipment that is essential. The club has a selection of mallets that beginners are welcome to use, but most people who take up the game prefer to have their own mallet. New mallets vary in price from about £100 to £400. They last for ever if looked after. Other equipment you may need are a timer (many people use the kitchen variety) and a coin to toss.
As far as clothing is concerned, you must have flat soled shoes to avoid damage to the lawns. White clothing is only worn at Nailsea for competitions, but there are a couple of old and prestigious clubs that insist on whites at all times. Waterproof overtrousers and a jacket will be invaluable at some point. In competitions we do not stop for rain!