For men or women?
Men: lounge suit, collared shirt, tie. Oxfords/brogues.
Women: smart trousers or pencil skirt. Or block coloured pencil dress. Blouse, shirt, or plain t-shirt. Jacket optional. Shoes: closed toe, options include courts, ankle boots, loafers, brogues. Unobtrusive jewellery. Look at The Fold for inspiration.