Minecraft wiki entry for Door-based_iron_golem_farming, associated text: at least 1100 cobblestone (about 18 stacks)
64 doors (6 wood per 3 doors=128 wood planks or 2 stacks)
18 water buckets (or 2 water buckets to make an Water Spawner)
1 lava bucket
4 signs
2 hoppers and 2 chests (This is for the option to use hoppers to collect items when you are away from the farm)