Which 5* to r5 or 6* to r2?

Gnotnus

I'm stuck in 6.2.2 and haven't finished Variant 1,2, 3, LOL, and AOL.
I assume I will need to rank them all in the end. But which champ should I prioritize to rank up for story quest and the variant?

Gnotnus

please share some thoughts. Since my golds are limited, I unfortunately can rank up only one of them at the moment..