Minecraft wiki entry for Things_not_to_do, associated text: Shovel (Stone or better) (For underground dirt and gravel patches)
Armor (Full Iron or better)
Pickaxe (Iron or better)
Sword (Iron or better)
Bucket of water
A stack of torches
Wood (For crafting more torches)
Building blocks
Coal (For the furnace and extra torches)
Chest or shulker box (to carry more items)
Food
Bed (To sleep when the player decides to return to the surface)
Furnace