Although your outfitter will send checklists for equipment and clothing, a few important items bear discussing.
Most companies rent bikes, helmets, and camping gear.
You may prefer your own familiar equipment, but renting eliminates cumbersome luggage and bike shipment fees. Renting also ensures having the right bike for the ride you choose. Though guides will fix flats and do repairs, it's still good to carry a tube, pump, and tool kit. Backpack hydration systems are invaluable. Fill them with ice to stay cool far into the day.