Highlighted weapons are free options.
As a free unit from Natlan, Kachina's value comes from being able to provide Off-Field Geo Application with her Skill, and being able to hold (4) to great effect. Kachina's Burst can extend the radius in which Turbo Twirly creates shockwaves, allowing you to hit enemies from a distance if you need to. While she can be built for damage, her personal scalings are rather low, and building her for damage isn't a requirement.
Kachina's [C1] allows her to restore 3 Energy whenever she picks up a Crystallize Shard, and mounting/dismounting Turbo Twirly absorbs nearby shards. The energy restoration can only trigger once every 5 seconds, but does help alleviate some of her Energy Recharge needs.
Turbo Twirly is considered a Geo Construct.
Kachina's Burst can bring Turbo Twirly back to her location if it is already on the field, allowing for a quick method of repositioning without having to actually ride Turbo Twirly. Her [C2] will summon a new Turbo Twirly if one isn't on the field instead.
If you are building Kachina as a low investment support, using the correct mainstats is not important. CRIT Rate should be prioritised further in this case when using for more consistent triggers.