Strategies for the Moon Lord?

While some of his attacks do pass through walls, a significant number are blocked by solid walls. Most importantly, his mouth laser and debuff tongue are blocked.

My arena is 5-6 blocks on either side to block the hands, and 7-8 blocks above to block the head, with a campfire and heart lantern.
My equipment is full Beetle (shell), with Charm of Myths and Ankh Shield. I expect the other accessories are up to you, as long as they are reforged for some defense.
My weapons are Solar Eruption and Stardust Dragon summon since they can attack through walls, with Phantasm and Nebula Arcanum for the second stage.
For potions I am using Super Healing Potions along with Regeneration and Ironskin. When I was using Greater Healing Potions I found I had to teleport to the Nurse to heal sometimes, but Supers enabled me to stay at the arena.

With this set-up I'm able to comfortably defeat the Moon Lord solo.
Hopefully these tips can bring you success too.

I simply used beetle armor (any armor is fine, as long as you have >75 defense). I also built a house that had a platform roof and moved the nurse in so I could always get a heal. I used a stardust dragon and a vortex beater with chlorophyte bullets so I could stay very far away. the defense is mostly used to absorb his head laser. Always try to get all 3 eyes under 3000 health so you kill them relatively quickly. Always stay near the nurse, and heal when you have the chance. When you have killed the eyes, congrats. You've basically won. Just don't forget to heal every so often.

Here's how I defeated the Moon Lord.

1. I had full Beetle armor.
2. I had full Golden hearts.
3. I had the Solar Eruption (This is key to this method.)

Alright, let's begin.

1. Build an Asphalt skybridge. (Asphalt makes you run faster, Stone + Gel)

2. Build a small house at one end of the bridge, make sure the nurse is assigned to it.

You're practically all set right now.

Now you just need to kill the Lunatic Cultist, and the pillars.

-Tips-

Make sure to heal when you're health is almost at half or at half. You don't want to be at low health running to the nurse for health.

hopefully by the time you are reading this, you have already beaten the moon lord, and everything written here is null and void, if you haven't yet then I have some tips of my own

Starting off with gear, the first time I deafeated the moon lord, I had Beetle armor (with shell) Daybreak Ankh shield Frostspark boots Charm of myths Warrior emblem Fire gauntlet And every buff I could get I was also using super healing potions

My arena was a mincart rail that stretched all the way across my (large) world below the level wyverns spawn at, I was also using a mechanical minecart despite the fact that I was not in expert mode

As soon as I defeated the fourth pillar, I would teleport home and heal at the nurse, as well as pick up my buffs and get to the minecart rail. When the moon lord spawned, I'd use my buffs, then race past him on the minecart. Once I was a good bit past his hand on that side, id slow and try to match my speed to his, and I'd use daybreak on the hand near me. Once that hand went down, I'd focus the forehead, it has very distinct patterns, specifically, the eye opens while charging the phantasmal death ray, after it ends, it blinks, then it closes the eye and you get hit by the tongue, after the three orbs heal it or are destroyed it repeats. The fore head eye shouldn't be too much of a challenge, but you have to jump over the orbs the true eye of Cthulhu sends your way. Once this eye is down, just keep going, and wait for your potion sickness to wear off. Once your potion is up, reverse direction, you'll probably need the potion once you get past the hand. Go back to daybreak on the hand, and jumping the orbs (if possible). Once that hand is down, aim daybreak at his core and continue dodging the orbs.

That worked for me, and hopefully it'll work for you too

In my experience a good strategy to beating moon lord is pretty simple.

Preparations:

1. Have full beetle armor (Shell), a stardust dragon or cell staff and a solar eruption to their best modifiers, (I believe it's godly for the staffs and godly for the solar eruption) and set all accessories to warding.

2. Have a charm of myths and an ankh shield you can choose others.

3. for the arena create a stone 8x8 house in the sky (below wyvern spawning level) and add campfires, stone walls, table and chair, heart lanterns, and a small space to add a 2x2 section of honey and make sure the honey doesn't flow out.

4. Set the house to the nurse (she will eventually die but saves you once or twice beforehand). For other healing effects I used greater healing potions and a regeneration potion Ironskin is good to use to.

The fight:

When the Moon Lord spawns from emblem or defeating the pillars, make sure to be in your honey blocks and drink your potions. You now have 4 effects healing you. Remember that Moon lords debuff only stops life stealing effects. Drink healing potions when needed and use nurse before healing potions because you what to make the most of her being there. Summon in the stardust dragon of cell and use solar eruption to attack his three eyes (the solar eruption goes through blocks). Lower them all to really low health and when all are at that stage attack all of them to knock them out in a short span to lower the length of time you have to deal with the true eyes of cuthulu. You may have noticed that a lot pot his attacks are blocked by the stone walls around you and one of the main things is the true eyes lasers. If they are inside your room when they use this attack it will not block them as much. When the core is expose attack it with everything and don't stop unless you need a health potion and then go back to attacking the core again. Core is the easier part of the fight for me and what I love about this strategy is you don't have to focus on dodging. If this doesn't work for you I would try one of the other answers. I tried a couple and most are effective and fun.

Get the legendary terra blade(crafted with true Excalibur and true nights edge) and the pulse bow(bought from traveling merchant)with the venom arrows. Also get full beetle Armour and some good wings.