Ganyu is, in a way, a very easy and forgiving character to build when it comes to her Artifacts. Because she is a Cryo character, you can easily create Cryo Resonance with your party comp. This will help to make up for a Crit Rate deficiency. So when you choose Artifacts or weapons for her, you can focus all of your attention on giving her Crit DMG instead. This is perfect because the majority of her damage comes from critical hits.
Some Artifacts that you can consider for your Ganyu build are:
4 PC Blizzard Strayer
The Blizzard Strayer full set is the best set you can put on your Ganyu. It doesn’t matter if you run her as a main DPS or a sub-DPS. The 4-piece effect increases your Crit Rate against enemies affected by Cryo. There is a further increase if the enemies are Frozen, which means a 4-piece set can give Ganyu a 40% Crit Rate boost. Since all of Ganyu’s damage potential comes from her Cryo attacks, the enemies will always have Cryo on them. So you can focus your attention on her Crit DMG instead to maximize how much damage she does when she lands a critical hit.
4 PC Shimenawa’s Reminiscence
Ganyu’s Elemental Burst offers a 20% Cryo buff to anyone within her circle (Ascension passive), which applies to her as well. A 4-piece Shimenawa’s Reminiscence asks you to sacrifice that boost in favor of the set’s 50% DMG increase. Obviously, you would want to take 50% over 20%! Every time you use your Elemental Skill, your energy decreases. But your Charged Attack will deal much more damage. This is a perfectly fine exchange because Ganyu’s Burst is not her main source of damage anyway.
2 PC Noblesse + 2 PC Blizzard Strayer OR 2 PC Noblesse + 2 PC EM
If you are building your Ganyu as a sub-DPS in a Melt or Freeze comp, then you will likely put EM weapons on her. If you do so, your Artifacts can focus on increasing both her Burst and Cryo DMG. Her Burst is going to be the main source of Cryo application in a reaction party, and you can also focus on her base Cryo DMG if she needs to dole out attacks herself. For reference, until I collected all 4 pieces of Blizzard Strayer for Ganyu, she had Noblesse + Blizzard Strayer. Even though she was a main DPS, she was still amazingly powerful.
Genshin Impact is readily available on the PS4, PS5, Windows PC, and mobile devices. You can only pull for Ganyu in Genshin Impact during the Adrift in the Harbor Character Event Wish.