Honestly - I wouldn't even bother until you have champs that are either: A) strong enough to 3* the entire Nightmare campaign (perhaps with the exception of 12-7, since that fight is just stupid), or B) strong enough to solo farm 12-3/12-6.

For that particular fight, you shouldn't really have any major troubles - just run two red champs, ideally either both running lifesteal or with one as a healer. If you post your roster I can see which would be ideal

i

This is my 

Royal guard, Apo(tanky and fast), Galek, Samar??????Best I could imagine. Maybe fb instead of samar???

you should be spending exactly this much energy in NM campaign..... 0

Yeah you are nowhere near close enough to being able to 3* Nightmare at the moment. I wouldn't spend any time or energy on it.

Lol my apo is a wet noodle

my current team is:

Samar (lead), Galek, Jizoh, Quargan/Apo (affinity)