Aloy

5★

CryoBowOff-field Damage

TL;DR

Aloy's Burst is one big lump of Cryo damage on a 12 second cooldown. Her Skill scatters little bombs that chip at enemy attack while handing your team 8% attack for 10 seconds. So most of the time you press Skill, wait for the bombs to go off, then press Burst. She can also stay on the field and work up an ice state for her Normal Attacks, which is fiddly enough to treat as a bonus rather than the plan.

Rotation

Skill (E) to throw the bomb. It bursts into smaller bomblets that go off on contact or shortly after.
Swap to anything that pulls enemies together, so more of those bomblets land.
Swap back and press Burst (Q), which is her biggest single hit.
Go again when the skill returns, every 20 seconds.

Abilities

Skill (E)	Throws a bomb that explodes on impact for Cryo damage, then splits into a spread of bomblets. Anything they hit has its attack cut for 6 seconds. Each hit also feeds her stacks. 20 second cooldown.
Burst (Q)	Lobs a cell of Cryo and shoots it out of the air for one heavy AoE hit. 40 Energy on a 12 second cooldown, so it comes back faster than the skill does.
Her stacks	One per bomblet hit, at most one every tenth of a second. Each stack boosts her Normal Attack damage. The fourth one clears the lot and starts her ice state.

The one mechanic to understand

Four stacks flip her Normal Attacks to Cryo.

At four stacks everything clears and she gets 10 seconds of an ice state, where her Normal Attacks hit harder still and count as Cryo damage instead of physical. Her Cryo damage bonus also climbs 3.5% a second up to 35% while it runs. She cannot pick up new stacks during it. Getting there means landing four separate bomblet hits, which is why enemies bunched together make such a difference. Her stacks also drain away 30 seconds after she leaves the field, so there is no banking them between fights.

What actually matters

The two or three real decisions. Everything else is noise.

Energy Recharge for the Burst. It costs 40 Energy with only her own skill particles paying for it. Roughly 150% has it ready every rotation if she is your only Cryo character, less if you have a second one.
The attack buff comes from the skill, not the Burst. Picking up a stack gives Aloy 16% attack and everyone else 8% for 10 seconds. Cast the skill before you swap to your damage dealer rather than after.
The bomblets have to land. They scatter, so a lone enemy in an open field eats two of them and a packed group eats all of them. No hits means no stacks and no attack reduction.

Gear

A build that works. KeqingMains lists every other option.

Weapon	Crit, plus enough Energy Recharge to keep the Burst coming. Sacrificial Bow is the nicest standard banner pick because its passive can reset the skill, which is the only thing generating her Energy.
Artifacts	4-piece Blizzard Strayer if your team freezes things, since the set hands out free Crit Rate against frozen enemies. 4-piece Noblesse Oblige otherwise, which puts 20% attack on the party every time she bursts.
Main stats	Attack sands, Cryo goblet, Crit circlet. Move the sands to Energy Recharge if the Burst is not ready when you want it.

Works well with

Pyro

Hydro

Pyro if you want to melt her Burst, Hydro if you would rather freeze everything. The attack buff she hands out is element blind.

Don't bother

Constellations. Hers are locked and always have been, so C0 is the whole character.
Chasing the ice state if she is only on the field for two buttons. It does nothing for her Burst.
Elemental Mastery, unless you are deliberately dropping her Burst onto a Pyro aura for melt.
Physical damage builds. Her Normal Attacks only become interesting once they have turned into Cryo.

Want the full theorycrafting version? Read Aloy on KeqingMains.