How to build Diluc (by a Diluc main)
a thread;

First we need to undestand how diluc works
He is a pyro claymore character, who benefits from pyro damage bonus and crit damage the most, since his crit rate gets increased with each ascension, crit dmg is great for him :)

LEVEL 80 DILUC AND ONLY 1.8K ATTACK???
yes! diluc is one of the few claymore users that don't benefit from pyshical damage
You'll want to focus crit damage for him, on the weapon and the hat*
a level 80 diluc will have 19.2% crit rate by default

*if you dont get artifacts that boost your crit rate to around 45% - 55% on their secondary stats, try to get a hat with crit rate or a weapon with crit rate (serpent's spine)

why 45% - 55%? that is the perfect amout of crit rate on this game.
50% will grant you that half of your attacks will crit, thats amazing!
but if you get more that that, its a waste and you could use crit damage instead

now for the artifacts
you'll ALWAYS want a 4 piece witch of flames
since this artifact set is hard to farm, 4 piece gladiator can be used until AR45+
the witch of flames set is a game changer for diluc, since his abilities have a low cooldown time and they are his main dmg source

You'll want to focus Attack on the sands of eon, crit damage or rate on the hat depending on your weapon and sub-attributes and on the feather and flower you will try to get crit rate on their sub-attributes

The goblet is a no brainer:
Pyro DMG bonus all the way.
the goblet's set doesnt matter since you'll already have a 4 piece complete

Now for the weapons:
you have 4 options
1- the best is the wolf's gravestone, the stats are amazing and if you have it, use it

2- the second option is the prototype archaic
its a great f2p weapon that boots your attack, overall really good

3/4
you can use the serpet's spine (battle pass) if you're lacking CRIT RATE or the Blackliff slasher (from the shop) if you're at a great crit rate already and wants more CRIT DMG (i personally use the blackliff and it does wonders for me)

For talents
level up the searing onslaught and the dawn talents as much as you can.
the normal attack doesnt matter that much, its the last one you should level up

for comps:
If u have bennett you're set. he heals, boosts your damage on the elemental burst and since he's pyro, you'll get a 25% attack bonus with both on your party
other characters like kaeya, beidou, fischl, barbara and etc that can help him get elemental reactions are great

with all of these you can easily get 8-20k damage on each activation of his normal skill and 34k+ on his elemental burst
with bennett's ult, melt reaction (2x DMG) and food, you are able to get 180k on his elemental burst, if you're lucky with crits

That's all! hope this helps :)
feel free to ask any questions if you need!