If you can learn to play her. If you don't get the hang of her or simply do not enjoy her playstyle, you are wasting a gem. I would never use rare resources on a champion that I'm unfamiliar with. I do my best to learn the champion 1st, and if I feel I can play them and/or like the style of their mechanics, only then I go for it.
As a sidenote, I do have a naturally duped 5* Ghost, but she sits at R3 because I can't stand playing her.
Ghost is awesome but she doesn't really need an AG. Save it for other champs that need it
there's not a lot of competition for it in the tech class tho. I'd use a tech gem on her over pretty much everyone including people like sentinel, star lord, dh, and sparky
Comments
As a sidenote, I do have a naturally duped 5* Ghost, but she sits at R3 because I can't stand playing her.
I'm still learning but here's where I'm at with her. Both fights has been easy.
I started messing around with 4* duped ghost to test.
My 5* ghost is R5 sig 180 now.
Test and decide for yourself but I doubt you'll be disappointed with a duped ghost.