Not much is available on the island
Luggage and bags: If you are on a day trip, take everything in a small day sack, and don't take too much as you will be walking a lot and have to carry it up the steep hill.
For those who are staying overnight, there is a 20kg limit. The lugagge will be brought up to the top from the boat for you by a tractor.
Clothing/Shoes/Weather Gear: Good, comfortable walking boots with a good grip and ankle support are a must. Bring rain gear, as the weather can change rapidly out here.