Qiqi has extremely strong healing capabilities, but it comes with the drawback of 0 way to battery herself pre-[C1] and no other meaningful way to support her team through her kit alone. Her A4 allows her to apply her healing talisman with her Normal Attacks which has a 30-second cooldown, and scales with her Burst talent. Energy Recharge will greatly benefit Qiqi, however you should not need to Burst every rotation.
Regarding Weapon Choices:
Due to Qiqi's extremely high Energy Recharge needs and inability to generate energy for herself, Energy Recharge weapons are prioritized.
Sacrificial Sword: This is Qiqi's best option for maintaining Skill uptime, assuming the Frost Herald is able to hit an enemy. Should the weapon proc, wait for the Frost Herald to disappear before using her Skill again.
Favonius Sword: This weapon can place higher if the team values the particles generated from it. Otherwise, it is preferred to use or other available options.
Peak Patrol Song: Thanks to Qiqi's high base Flat DEF, you can get a meaningful amount of the buff from this weapon. While using this weapon, you must Normal Attack twice to activate the passive. DEF% stats can be considered if your team does not struggle with survivability.
Amenoma Kageuchi: This weapon will significantly improve Qiqi's healing capabilities, however, it takes lower priority over weapons that provide Energy Recharge.
Regarding Artifact Choices:
Sets
Tenacity of the Millelith (4): This option is recommended only when paired with to be able to maintain uptime on the ATK% buff from the set.
Scroll of the Hero of Cinder City (4): This set is a great option if Qiqi is placed in a party with a character from Natlan. Do note that she may have a rough time triggering an elemental reaction if you are solely using her Skill.
Ocean-Hued Clam (4): This ranking assumes Qiqi does not get her Burst up often and is instead relying mainly on her Skill for healing. If she is in a team which funds her enough energy particles, or if she acts as the on-field DPS, this set can overtake (4).
Substats
CRIT Rate: Only recommended if using a Favonius weapon.