Ningguang's Skill has a 6 second internal cooldown on generating energy, so for the sake of maintaining Burst uptime, wait 6 seconds to cast again if you need energy. It also breaks when cast on top of another Geo Structure, you can intentionally use a structure to break your first screen.
Regarding Weapon Choices:
Memory of Dust: This weapon performs slightly worse if Ningguang does not have a shielder or consistent Crystallize uptime.
The Widsith: This weapon performs better than at [R5].
Solar Pearl: This weapon performs better than at [R5].
Flowing Purity: This weapon performs worse than if you cannot clear the Bond of Life from its passive.
Regarding Artifact Choices:
Sets
Nighttime Whispers in the Echoing Woods (4): This ranking assumes Ningguang consistently has a Crystallize shield.
+20% ER set (2): This set performs worse than other options when Ningguang does not need to build Energy Recharge.
Husk of Opulent Dreams (4): This set performs on par with (2) / +18% ATK set (2). With its inclusion in the strongbox, it has become a strong generalist option.
Thundersoother (4): This set is one of Ningguang's best options in teams where Electro Auras remain on enemies for the entire rotation.
Lavawalker (4): This set is one of Ningguang's best options in teams where Pyro Auras remain on enemies for the entire rotation.