Lucian Build (Help)

Hi all!

I bought Lucian, but i still dont understand his builds. From what i understand we have two main builds:

-Blade of the Ruined King + Black Cleaver + Phantom Dancer

versus

-Essence Reaver + Rapid Firecannon + Infinity Edge

Could you explain me the pros and cons of those builds? I'm trying to understand them... Which do you think is the best build for Lucian?

Thanks to everyone that can help!