Ganyu

Ganyu is a charge shot focused Cryo archer. She can charge up her bow up to level 2, causing an additional attack that deals almost double the damage. Most of her strength lies in the charge shot, which means that it's not limited to a skill cooldown, does not consume stamina, and no hit drag/delay whenever you're attacking an enemy. Her elemental skill and burst mostly serves utility purposes. The skill gives her a layer of safety when aiming since it has taunting abilities, while her burst is a great supporting skill for Cryo application, or just good additional damage.

Her kit mostly focuses on her abilities, and not empowering her normal attacks, and all her abilities deal Cryo damage, so you will likely want to build her with at least 2 piece Blizzard Strayer for the +15% Cryo damage bonus. Her 1st ascension passive combined with 4 piece Blizzard Strayer can be good as well, giving her 40% crit rate, or 60% on frozen enemies, even if you don't have any crit rate from your gears. But since it doesn't increase damage, you will want to focus more on increasing your crit damage with this setup, or just use 2 piece Gladiators Finale for standard DPS build instead.

Alternatively, if you only want to focus on her charged shot and melt damage, you can build her with 4 piece Wanderers Troupe for 35% increased charge shot damage, with some elemental mastery bonus from the 2 piece bonus. 4 piece Heart of Depth if you want a farmable version of Wanderer's Troupe. The 2 piece bonus effect won't be useful, but the 4 piece bonus will be a nice attack bonus.

For weapons, Amos Bow may potentially be her best in slot weapon because of its high attack increase, making her capable of dishing out high numbers, especially with melt reaction. Skyward Harp is still a solid option because it gives crit related stats, which works well with the 4 piece Blizzard Strayer. Blackcliff Warbow has good potential in certain situations if her damage starts to get high enough. If your only options are the craftable ones, then Prototype Crescent is better than compound bow.

This will depend on what kind of support type you want her to go for. If you play her as a support DPS, 4 piece Wanderer's Troupe is good especially if you have a Pyro in the party, Blizzard Strayer if you use another Hydro character in the party. Otherwise, 2 piece Blizzard Strayer and 2 piece Gladiator's Finale / Noblesse Oblige for convenience purposes.

If you only use her for the elemental skill or burst to enable combos, 4 piece Noblesse is more recommended, with energy recharge as the main stat for the hourglass piece. Or just 2 piece The Exile with 2 Scholar for consistent burst uptime and very cheap investment.

Sacrificial Bow is the cheap and effective support weapon for energy gain, and good utility because the skill keeps taking enemy's attention. If you want the burst to be able to do some damage, then it's The Stringless.

For charge shot playstyle, it will help if you have at least a Hydro character in the party to freeze enemies. Mona is easily the best choice since her burst also increases damage towards enemies. Her skill also has taunting ability, so you can alternate between Ganyu and Mona's taunt to avoid getting targeted by enemies. Other Hydro characters are still acceptable options.

For some high power and potential one shotting ability, then you'll want to bring a Pyro character for a melt reaction. Bennett is the obvious and easy choice for that since he boosts your on field character by a considerable amount.

Tartaglia can be a good pair to perma-freeze multiple enemies. He also has a passive that increases normal attack talent by +1, to further increase Ganyu's charged shot damage.

Xiangling's burst can apply strong Pyro, allowing Ganyu's charge shot to get Melt reaction twice with each staff rotation.

Zhongli's shield can really help with some survivability since you won't get knocked back, or staggered, if you are hit when you are aiming. His burst petrify will also help you aim at enemy's weak point.

Both Venti and/or Sucrose are amazing options for Ganyu, especially if you give them a 4 piece Viridescent Venerer artifact set for the -40% elemental resistance. You can infuse their Anemo bursts with Pyro, by using characters like Bennett, so that you can proc constant Melt reaction from each charge shot. Venti's burst groups up multiple enemies, causing Ganyu's icicles from her burst to target the same location multiple times.

Normal Attack
Perform up to 6 consecutive shots with a bow.

Charged Attack
Perform a more precise Aimed Shot with increased DMG.
While aiming, an icy aura will accumulate on the arrowhead before the arrow is fired. Has diffferent effects based on how long the energy has been charged:
・Charge Level 1: Fires off an icy arrow that deals Cryo DMG.
・Charge Level 2: Fires off a Frostflace Arrow that deals Cryo DMG. The Frostflace Arrow blooms after hitting its target, dealing AoE Cryo DMG.

Plunging Attack
Fires off a shower of arrows in mid-aire before falling and striking the ground, dealing AoE DMG upon impact.

Leaving a single Ice Lotsu behind, Ganyu dashes backward, shunning all impurity and dealing Cryo DMG.

Ice Lotus
・Continuously taunts surrounding enemies, attracting them to attack it.
・Endurance scales based on Ganyu's Max HP.
・Blooms profusely when destroyed or once its duration ends, dealing AoE Cryo DMG.

Coalesces atmospheric frost and snow to summon an Ice Soul Gem that exorcises evil.
During its ability duration, the Ice Soul Gem will continuously rain down shards of ice, striking enemies within an AoE and dealing Cryo DMG.