Best SSF build?

Yeah but you can't START with it, which I guess is the point of this question?

My starter this league was a Flame Totem Chieftain (see my characters) and I admit to being underwhelmed. Again, with respect to your question, you have to build on Fire/Elemental/Spell/Projectile damage on items/tree. Speaking of that, I really have never paid much attention to Double Dipping (right before it gets changed, I never said I was good or smart) so I am going to look into investing more in Fire/Elemental/Projectile damage rather than Spell damage and see where I can take this build.

My starter and what I currently play is FB-Elementalist. No unique needed, can clear anything fairly easy. Prime example of how double dip dmg is broken.