Although I do enjoy answering build questions, you’ll really need to be more specific. Anyways, you just asked how to build Kaeya. . . So here’s the giant infodump I spat out.
I first want to get this out of the way: I strongly, strongly, strongly believe you do not need to worry too much about builds until mid to late game, or around AR30ish. Maybe AR25 at very earliest. This is because, before that point, you will not have access to artifacts, weapons, and other materials that are worth investing in. Three star weapons, with very few exceptions, become almost obsolete in endgame.
This does not mean that you can’t upgrade three star weapons or artifacts, but that you should not be seriously investing resources into them. A better use of resin and mora would be Ley Lines, weapon enhancement domains,and talent book domains. I highly recommend not doing artifact domains until at least AR40, if not AR45, which is when you begin to unlock five star artifacts. I don’t know why some people are so eager to begin artifact farming. Take it from me, eventually you will be doing artifact domains til the cows come home.
I do want to say that builds aren’t important until later in the game. Around AR35 or so is when you might begin equipping better artifacts and sets on your characters, but don’t begin to seriously invest til later.
Okay? Good. Let’s talk early game (pre AR25). Do, what do you want on your characters then?
Basically, don’t sweat it too much. Focus on Attack percent main stats if you can, at that point in the game you just need to kill enemies. If you have a character whose abilities scale with some other stat, for example Noelle’s shield scales with Defense and Barbara’s healing scales with HP, the equip that instead. But don’t bother with set bonuses or substats. You will be fine without them.
Now, mid to late game. This answer is focusing on 4 and 5 star artifacts and weapons for players after AR35 or so.
The very first major choice you have to make when building any Genshin Impact character is whatt they will be built for. Usually this is one of two choices: DPS (smacking enemies to death) or support (helping the party in some other way, like healing or making the DPS smack enemies to death faster).
Kaeya is not a healer, congrats, you have that decision made for you. Yes, one of his passive talents heals him a little, but that’s not enough to justify building him as a healer. But still, DPS or support?
I’m not going to try and talk you out of building Kaeya – I personally don’t think he is the best of characters but he is still solid, and in my opinion the best of the starter characters if you don’t include the Traveller.
Let’s begin DPS. Now you instantly run into another question: do you want him as physical or cryo DPS?
You need to invest in his basic attacks no matter what route you’re going with if you want him as DPS. Give him a decent sword.
Unlike, say Razor, who is almost always built for physical damage, you can go both ways. Kaeya has one of the highest damage multipliers for his basic attacks out of any sword user in the game. So running him as DPS with a superconduct team (to reduce the physical resistance of enemies) makes perfect sense. His quick applications of cryo are very useful here, and if you pair him with someone like Fischl, who has very reliable electro application, you can have near constant superconduct reactions going.
For a physical build, you shouldn’t focus on cryo — Kaeya’s skill and burst are mostly there for the elemental debuff, their main purpose is not damage. Instead, you want as much physical damage as possible.
For a weapon, Prototype Rancour from the blacksmith is a good choice — you get one for free by finishing the Archon quests, and you can craft more to refine if you want. It has physical damage bonus as it’s substat, which is what you’re after.
For artifacts, at least 2 pieces of Bloodstained Chivalry for the 25% physical damage bonus. You can go full Bloodstained if you plan on using charged attacks a lot, or combine it with 2 pieces of Gladiator’s Finale for the 18% attack boost. Or you can go completely Gladiator’s, which is a pretty solid choice for any melee DPS.
You want physical damage as main stat on the goblet, with Attack %, Crit Rate, and Crit Damage as substats. Crit stuff gets better than Attack as you progress. Elemental Mastery and Energy Recharge are less important since this build is basically “hitting things hard with a side of ice damage,” but they’re still better than Def or HP.
For a cryo build, you have a few options. With the new set, Blizzard Strayer, that came out in the Dragonspine update, you have a lot more choices than previously. You can go 2 pieces Blizzard Strayer and 2 Gladiator’s, a general all-rounder build with a slight cryo focus (this comp — 2pc elemental/physical set and 2pc Gladiator’s — is pretty good for most DPS characters, but it is not the best in slot for all of them). This isn’t really a true cryo build though, more like a cryo-physical hybrid.
Or you can go 4 piece Blizzard Strayer, run a freeze team with a hydro user like Barbara or Mona, and gain 40% Crit Rate when your enemies are frozen. This is probably the better option, because having Crit Rate built into the set bonus lets you have some leeway with artifact substats and weapons.
And artifact substats are the same as above mentioned, but Elemental Mastery and Energy Recharge are more important here because you need more uptime on your skill and burst, as they are much larger sources of damage than with a physical build.
Most characters do better in an elemental build than a physical. Razor, again, is one of the few exceptions.
As for weapons — I’m not listing all the possible swords here. You want Crit Rate, Crit Damage, or Attack Percent for a substats, and the passive should be something that deals damage. Read the descriptions carefully and make sure you can use them — if it requires a shield to activate, you need have a shield character.
Blackcliff Longsword from the Starglitter shop or Iron Sting from the blacksmith are okay. Iron Sting’s passive is nice, because it increases your attack after dealing elemental damage — Kaeya’s skill has a short cool down so this should be up almost all the time — but the substat is elemental mastery, almost useless because the Frozen reaction does not deal any damage. Breaking the ice with a claymore is what deals damage. The Black Sword from Battle Pass is also a solid pickup, good for any sword DPS, and one of Keqing’s best weapons.
As for three stars, you can use Cool Steel or Harbinger of Dawn, but know three star weapons have a lower base attack than four or five stars. Neither of the weapons I listed are worth seriously investing in, as they fall off in late game.
Now, support Kaeya. To me, Kaeya screams support because he gains energy recharge as he ascends. I am planning to build him as support eventually, as my only other cryo unit is Chongyun, who makes team comps a little more difficult because of how his skill works.
Support, you want cryo bonus, so again, at least 2 pieces Blizzard Strayer because supports are mostly there for their skill and burst. Energy recharge is another important one for his burst, elemental mastery too. Don’t bother with physical damage here, you won’t be basic attacking with him enough to justify it. For Kaeya, Energy Recharge isn’t as important because he does get it when he ascends, but having a little extra doesn’t hurt.
Noblesse Oblige, which gives a nice damage boost to his burst for the 2 piece bonus and to the entire team for the full set, is also valid. Note that the four piece effect doesn’t stack, so if you have a Noblesse unit in your party already that won’t be as of much use. This is useful because, unless you swap party memebers a whole lot, Kaeya won’t be on the field every time his elemental skill is available to use, so most of his damage will probably come from his burst.
You can mix and match artifacts and weapons to your heart’s content here, this is only meant to be a general outline. (Sub DPS is another option I didn’t cover, but you’d basically mix DPS and support builds.) Again, you don’t need to worry about building characters until you’re mid to late game.
That’s all, thank you for reading and good luck with the artifact substat rolls.
I forgot to add — talents. DPS will need his basic attacks leveled up first, support wants his skill and burst more.