To confirm you mean NM 6/3 campaign? After beating brutal, I would stop with progressing with the campaign unless it's to three star each stage (same with normal and hard). You should be focusing on building an arena team and developing a champ to farm 12-3 brutal. From there you can level up food/chickens to feed other champs.

For arena, I'd go with HK-->Warmaiden-->Galek--> Relickeeper or Seeker --> HK -- Warmaiden --> Galek in that speed order. I'm not sure about Galek as a 12-3 farmer. You may have to pull someone else for that. I would not 6 star Jizoh, not a great champ. Same with Yaga. Kaiden is a great champ so put him on your que list. 

I agree, forget Nightmare campaign for now. Galek could certainly farm brutal 12-3 - but perhaps Relickeeper is already doing that? If not, yes, you'd need to level Galek. 

Best champions are Kaiden, Seeker and Frozen Banshee - those are all definite 6*s. 

big  thx  for  help  guys!  now  i  have  a  plan  for  the  nect  60  days🙈