Firstly, I usually jungle though this build has worked for me playing top too.
Boots, 3x hps
Lantern (starting with razor)
Phage
Hex Drinker
Frozen Mallet
Maw
Force of Nature/Sunfire (depending on who's doing well on enemy team)
and then whatever you want... more tanky: GA, more dmg: bloodthirster or last whisper, more mobility: PA
That's just how I build him. I'm sure there's better builds but this gets me high ad, high survivablity and enough sustain with his w passive and lifesteal from lantern.