First of all, start with boots of speed and 3 health potions.
After quite some time of farming top lane go and get your self "Sunfire Cape" also if you have enough then buy "Giant's Belt" to build up to "Warmogs" later on next you should think about building either some magic resist or more armor depending on what your up against on top lane or wether your going up against their mid guy alot then buy "Spirit visage" for magic resist or "Warden's Mail" for armor.
Now we come to either "Warmogs" or "Guardian Angel", depending if you want/need to live after teamfights then go for "Guardian Angel" or try and survive the teamfight long enough so your team mates can kill off their team then go for "Warmogs".
and last item go for "Randuin's Omen".