Nahida can provide both damage, Dendro application, and buffs to her teammates. As such her build is focused on both maximizing her buff and her damage simultaneously.
Regarding Weapon Choices:
Wandering Evenstar: If teammates significantly benefit from the Flat ATK this weapon gives, it has the potential to rival .
The Widsith: This weapon tend to perform better if Nahida is played on-field.
Skyward Atlas: The fewer the reactions Nahida triggers, the more potent this option become.
Lost Prayer to the Sacred Winds: This weapon tend to perform better if Nahida is played on-field.
Memory of Dust: The fewer the reactions Nahida triggers, the more potent this option become.
Solar Pearl: This weapon tend to perform better if Nahida is played on-field.
Favonius Codex: This weapon has the potential to rival if Nahida can actively trigger the passive multiple times by attacking on-field. also has the potential to be a good weapon on Nahida in teams where her Energy Recharge requirement is high, or if your team values the additional particles.
Hakushin Ring: This weapon should only be used if Nahida is used in Quicken or Hyperbloom teams.
Thrilling Tales of Dragon Slayers: This weapon sacrifices a lot of Nahida's personal damage for buffing potential. Generally not worth the trade, but can be usable in teams where Nahida's damage share is already low.
Prototype Amber: Only to be used if the team otherwise lacks survivability.
Regarding Artifact Choices:
Nahida has several viable combinations of main stats. The general rule of thumb is that the more Elemental Mastery Main Stats you use, the better ATK%/Crit weapons will perform relatively.
Sets
Deepwood Memories (4): This is her best set if no one else is wearing this set.
Tenacity of the Millelith (4): In teams where Nahida's damage share is relatively low and there is another holder of and/or no need for the set at all, this can be Nahida's best set.
Flower of Paradise Lost (4): This set is niche, but very powerful in Bloom teams where Nahida triggers the Bloom reaction.
Substats
Energy Recharge: Prioritize until requirements are met.