Who should I make 5☆ first

soleil or Erika is good choice.

Soleil, Effie, Nowi. If one of them has good IV's

Tharja running the klinge. Lol

Not sure who all you have already at 5* but I’d say of the list you have, Effie and Nowi have the most promise (not sure how many merges Nowi has, but if she’s at a high 4* merge level then go Effie)