How do you make Black Rose work?

I see people everywhere claiming that the Black Rose comp is one of the best, if not the best comp right now, but every time I try it, I lose BADLY. I always keep Elise in her human form and build Nashor’s, Shojin, and Gauntlet on her—maybe that’s my mistake, and she should stay in spider form?

Cassiopeia honestly feels like a waste in my hands. Even fully equipped, she can’t outdamage an unequipped Elise. My only success comes when I get an early Heimerdinger, but at that point, it feels better to just build Visionary outright rather than wasting time on a Sion who’ll die in 4 seconds.