Wisp is not only a support but also crowd controller and damage dealer, why focus on one task when you can do much, much more?
Her signature weapon is quite a gun! So here is my build for her Fulmin.
I've changed her completely useless Sol Gate for Gloom, to make her a real melee beast. She stuns enemies, she slows enemies, she blinds enemies, she massacres enemies. This is melee Wisp, this is real monster. Use with pleasure.
Suggested arcanes are Avenger & Energize to give her Critical Chance for both range and close combat weapons and make her spam all those skills.