When you are asked to dress in casual attire, avoid the urge to be a sloppy dresser. Rather than wear acid-washed jeans and a faded T-shirt, slip into some dark wash jeans and a stylish top if you are a woman. Men can wear jeans or khakis and a button-front or golf shirt. Make sure all attire is pressed and free from wrinkles.
You may add a cardigan or pullover sweater, lightweight jacket or windbreaker, or a blazer. Sweatpants are never appropriate for anything but working out or lounging around the house. Footwear should be clean and polished – a pair of ballet flats for women and loafers for men. Athletic shoes will work for an ultra casual event, as long as they are clean and without holes. A nice pair of polished boots is also appropriate.