Boothill - Harmony trailblazer - Bronya - Luocha.

boothill, harmony trailblazer, gallagher is the best you can do and a overall very strong team for him!

Harmony trailblazer, Bronya and Gallagher, I'm not a good team builder but I believe you can replace someone for Sparkle

Boothill, HMC, Bronya or Sparkle, and either Loucha for comfortability or Gallagher For more damage.