Minecraft wiki entry for Defeating_a_dungeon, associated text: Torches or other light sources to disable the spawner, as many as possible
A sword, stone or better, preferably enchanted with Sweeping Edge‌[Java Edition only], Sharpness, if possible (Knockback and fire aspect are optional)
A full set of iron or better armor (enchanted if possible) (If you are experienced enough, and is not playing on hard difficulty, you don't need armor.
A pickaxe
Nutritious food like bread or steak
Plenty of cheap building blocks, such as dirt or cobblestone
A golden apple (optional)
A shield (optional)
Potions (optional)
A lava bucket (optional)
A water bucket (Always needed for mining trips)