For suiting, dress shirts and ties aren't required, nor are matching suit pieces. You can mix and match suit separates, work a sweater into the outfit (a great option for a fall wedding), or leave your tie at home. A suit jacket is not required (although it might be nice to have a jacket at night). For those wearing dresses, something in a midi-length is perfect, though you're also welcome to experiment with jumpsuits, rompers, and separates. Think elegant, but not too over the top.