5 star upgrade

What units do you have, I mean GHB units are always an option. Dragons like Nowi and Adult Tiki too.

Honestly I'd just promote your favorite/most used 4* units until you have a pretty solid 5* collection. most units are pretty usable these days but it's most rewarding if you enjoy using them.

Define good? Are you looking for a 4* unit to upgrade for the fun aspect, or are you looking to upgrade to have a good unit for more general use?

How far are you willing to go to invest in said unit that you upgrade?

What units have you been thinking about upgrading?

Do you have any merge projects?