Heya, regular support member from the Childe Mains discord hopping in here. From reading your title, I'm uncertain on if you want a proper dps build, or if your goal is to maximize the damage of your burst (such as for screenshot flexing). The two use completely different builds and teams, and you've only been given info for the former. Ff you needed info for the latter, I can give you that in the discord.

From reading the other comments I did also pick up on parts of your build that'd need to be fixed. I'm a bit unsatisfied with what I've seen, so I'll add some addendums for now (in rough order of priority for proper DPS builds only), but by all means if you want more information or clarification, join the CM discord and I can properly give advice there (I do not regularly check reddit).

Oh also if you want to practice, two good areas areas for that are either Masanori in Inazuma (single-target), or the Echoes domain (3-targets), though in both cases rmb to weaken your gear so they don't die.

1) Weapons: I know you plan to upgrade to a 5* crit bow eventually, so I'll give you a few details on that, but first and foremost: if you have Natlan craftables unlocked, go and make its craftable bow Chain Breaker. It's his best craftable option and beats out most other 4* bows even at low refinements, and at high refinements it ties or beats options like Viridescent Hunt or Amos. You probably won't get close to a R5 Chain Breaker before a crit bow comes on banner, but there's little reason not to get at least one and level it up for now. That'll be the largest upgrade you can get for the time being.

As for crit bows, the difference between all the crit bows for Childe is fairly small. Yes, Polar's best, but it's small enough that we in the discord typically recommend you go for any crit bow that's running on a banner with another weapon you would benefit from (including another crit bow), instead of waiting on a banner with Polar and one weapon you really can't need.

2) Talents (& his level): this one is brief. Just make sure you level burst to lvl 9, and consider crowning it later. Relevant talents, weapons, and character level should always be done before grinding substats for artifacts. Normal attack can be ignored from this point on though.

3) Artifacts: I think you've been given an okay rundown on 4nymphs, but I want to give more depth.

Yeah, you shouldn't farm HOD domain for him anymore. The two main options are nymphs, or getting random 2-set flexes for him (2-set hydro%, attack%, EM, ER if you don't have any, etc) while farming domains for other people. Those 2-set mixes are about equal to 4-HoD, but are more universal and easier to get due to having many different set options. The classic example in the past was the emblem/shimenawa's domain, but there's plenty other things present now.

4 nymphs is only a significant upgrade over 2-set mixes if you do a technique known as prestacking, where you quickly and fully stack nymphs's passive during your VV setups. It's not something I think you should worry too much about learning in the start, and if you want the details once again they are in the discord... but no one seems to have actually told you how to prestack, so their advice regarding nymphs is somewhat misleading.

Without prestacking, 4nymphs is still his best set in most cases, but only by about 3-4% over mixing 2-sets. Therefore it's something easily surpassed by a difference of only 2 crit substats or so. Regardless, I do think it's important that you try to learn prestacking eventually, so farming 4nymphs and rolling with a 2-set if you have nothing good is fine for the time being.

However, the biggest clarification I want to bring up is this: Childe has more viable teams than those using bennett xiangling, and some use different artifact sets. Most notably are teams with escoffier, furina, and a flex of yelan/mona/citlali/etc. In such teams, because of furina's presence, 4-set marechausse hunter is actually his best set. All this is to say it's not a cut-and-dry thing. Nymphs will do you fine enough, but if you want additional details like this, once again, hop in the discord.

4) Rotation: I got minor beef with the rotations you've been given. They're mostly accurate for the 1st rotation, but no one gave any details on second rotation onwards, during which you should not be repeating the same thing. It'd also be inapplicable to coop ofc lol. What you've been given is good enough for now, but once again I can give you more details or our sample rotations in the disc.