Guide
How the kit works
Start by setting up your teammates, then use Trail of the Qilin to dash backward and leave an Ice Lotus. It taunts nearby opponents and deals area Cryo damage when it is destroyed or expires. Its endurance scales with Ganyu's Max HP.
Use Celestial Shower when you want its continuous Cryo damage over an area. Harmony Between Heaven and Earth gives active party members inside that area 20% Cryo DMG Bonus, so another Cryo character can use the field too.
With Liutian Archery (NA), hold your aim until charge level 2 and fire a Frostflake Arrow. The initial hit and the bloom both deal Cryo damage, with the bloom hitting an area. After the first Frostflake Arrow, Undivided Heart gives subsequent arrows and their blooms 20% CRIT Rate for 5 seconds. Keep firing while you have a safe opening.
There is no need to cast the Burst in every situation. In a Melt team, watch the enemies' elemental status and choose when its repeated Cryo hits fit your setup.
Build and why
For Freeze, four pieces of Blizzard Strayer are the first set to consider: they give 15% Cryo DMG Bonus and 20% CRIT Rate against Cryo-affected opponents, with another 20% against Frozen targets. Four pieces of Marechaussee Hunter are another option if the team can change Ganyu's HP: each change gives 12% CRIT Rate for 5 seconds, up to three stacks.
For Charged Attacks, four pieces of Wanderer's Troupe give 80 Elemental Mastery and 35% Charged Attack DMG to a Bow user. Four pieces of Shimenawa's Reminiscence are also worth considering: after using the skill with at least 15 Energy, Ganyu loses 15 Energy and gains 50% Normal, Charged and Plunging Attack DMG for 10 seconds. That Energy cost can make the Burst harder to use.
Use ATK Percentage or Elemental Mastery on the sands, Cryo DMG Bonus on the goblet, and CRIT DMG or CRIT Rate on the circlet. Look for CRIT DMG, CRIT Rate, ATK Percentage, Elemental Mastery and Energy Recharge in substats. Account for the CRIT Rate from Ganyu's passive and your chosen set when balancing the stats.
The First Great Magic is the first weapon choice: it increases Charged Attack DMG by 16% and gives ATK based on party members with the wielder's element. Aqua Simulacra gives 20% damage when opponents are nearby, even off-field. Amos' Bow increases Normal and Charged Attack DMG by 12%, with another 8% every 0.1 seconds the arrow is in the air, up to five times. Prototype Crescent is a four-star option if you can hit weak points with Charged Attacks.
Leveling priority
For an on-field build, a good order is Liutian Archery (NA) first, Celestial Shower second and Trail of the Qilin last. The arrows are your repeated attacks, while the Burst deals continuing area damage. If you use Ganyu mainly for her Burst, consider raising it earlier.
For ascension, gather 420,000 Mora, 168 Qingxin, 46 Hoarfrost Core, 1 Shivada Jade Sliver, 9 Shivada Jade Fragment, 9 Shivada Jade Chunk and 6 Shivada Jade Gemstone. You also need 18 Whopperflower Nectar, 30 Shimmering Nectar and 36 Energy Nectar.
To raise all three talents to their maximum, you need 4,957,500 Mora, 9 Teachings of Diligence, 63 Guide to Diligence, 114 Philosophies of Diligence, 3 Crown of Insight and 18 Shadow of the Warrior. That is separate from another 18 Whopperflower Nectar, 66 Shimmering Nectar and 93 Energy Nectar.
Constellations worth it
Dew-Drinker (C1) is the standout constellation in the listed guide evidence. A level 2 Frostflake Arrow or its bloom lowers the target's Cryo RES by 15% for 6 seconds and restores 2 Energy to Ganyu. The Energy effect happens at most once per arrow, even if both parts hit.
The Clement is worth considering for its change to aiming: after Trail of the Qilin, the next Frostflake Arrow fired within 30 seconds needs no charge. The Auspicious, which you obtain on the way, gives the skill another charge.
Westward Sojourn is another upgrade to consider when the team fights inside Celestial Shower. Enemies in its area take 5% increased damage at first; that rises by 5% every 3 seconds to 25%, and remains for 3 seconds after they leave.
Cloud-Strider (C3) adds three Burst levels, while The Merciful adds three skill levels. Both can be skipped if you are content with the base kit; neither changes how you aim.
Teams
For Freeze, pair Ganyu with a Hydro character such as Furina or Sangonomiya Kokomi. Kokomi can also heal. An Anemo character such as Kaedehara Kazuha can use Swirl, while a second Cryo character such as Shenhe or Charlotte can take advantage of the Cryo DMG Bonus from Celestial Shower. Charlotte can also heal.
For Melt, consider Pyro teammates such as Bennett, Xiangling or Mavuika. A shield from Zhongli or Citlali gives Ganyu protection while she aims. Citlali is also Cryo, so she can use the Burst's Cryo bonus when active inside its area.
You can also use Ganyu for her Burst alongside another Cryo damage dealer. Place its field where that character can fight inside it, then swap to them while its ice shards continue to fall. Pick the remaining teammates around the reactions and protection the team needs.
Common mistakes
Do not release every aimed shot at charge level 1 if you want Frostflake Arrows. Wait for level 2 so the arrow can produce its area bloom. Avoid aiming in front of an approaching enemy without first creating space or using protection.
Do not count the 20% CRIT Rate from Undivided Heart on the first Frostflake Arrow. It applies to subsequent arrows and blooms for 5 seconds after you fire one. With Blizzard Strayer, check whether enemies actually have Cryo on them or are Frozen before counting its full bonus.
Do not ignore the 15 Energy cost of Shimenawa's Reminiscence when planning Burst use. If you rely on Prototype Crescent, remember that its ATK bonus requires a Charged Attack hit on a weak point.