Minecraft wiki entry for Nomadic_experience, associated text: An iron sword or better, preferably enchanted.
A bow, preferably enchanted, and at least 128 arrows, one arrow if the bow has infinity.
A full set of iron or better armor, preferably enchanted with Protection.
At least 32 highly nutritious food like steak, cooked chicken, or bread.
At least 2 stacks of expendable blocks like dirt or cobblestone for pillaring and building bridges.
This is required for all missions. It can prevent fall damage, allow you to climb obsidian pillars, and repel enderman.
A pickaxe, iron or better is used to mine end stone or the iron bars around the end crystals.
A few golden apples can be used for emergency healing. Optional.