I cant decide when i want to or if i wanna be a goul should i finish the quest anyway?

So as it says idk if i wanna be a goul yet but i only have 1 main quest left and should i get it completed like is there anything u get or stuff to do after completing it. I only havnt finished it cus i cant decide if i wanna be a goul yet and i dont wanna spend a 1000 atoms if i end up wantin to be 1 so whats ur suggestion?