Note – this is a brief overview, do your research before a real fight!
Armor and sword – only the best will do here! Enchanted diamond is the classic choice. Alternatively upgrade to netherite, if possible and available in your current version of Minecraft. An axe and shovel won’t be needed.
Bow – enchanted and with stacks of arrows, or the infinity enchant. Use to shoot down the crystals, and to help you damage the dragon, of course.
Food – take plenty for the journey and fight, and bring a few of your golden apples out for a much-needed bite.
Materials and tools – bring plenty of cobble, good shovel and pickaxe. Use these to quickly make your way up to and destroy the encased crystals.
Potions – Healing or regeneration and strenght are mandatory in order to ease the fight, and help you actually survive. Slow falling (or a bucket of water) is also useful to break falls. Note splash potions are faster to use.
Ender pears – you’ll need 12 eyes of ender for the portal frame, plus extra to find the portal, so maybe two dozen total. Likewise, a few ender pearls could save you in the end if you get knocked off the columns or islands.
Beds – optional, but will explode if you attempt to sleep in the end, dealing plenty of collateral damage when timed right.
Other – You could take empty glass bottles if looking to obtain dragon’s breath and the associated achievement. Both empty and dragon’s breath bottles are stackable to 64, making this easier.
Part of my concise inventory series: https://premiumminecraft.com/survival-inventory-layout-and-space-management/