Builds will depend hugely on where you're going and what role you're trying to play for your team. Jungle and Top Elise make great tanky assassins, since they don't have to build much damage in order to do a lot of damage (because of %health skills).
A sample jungle build would be: SoAG Sunfire Cape Spirit Visage Liandry's Zhonya's / Abyssal Boots of choice (either Sorc's, Merc's, or Mobility)
Top will be pretty similar to your jungle build, except you'll probably want to replace SoAG with another defensive item (probably Warmog's)
Mid Elise is far more offensive than the other 2: Zhonya's Liandry's Abyssal Rabadon's Rylai's Sorc's Shoes --- On the field of honor, the gods bearing witness to my glory, I will pull your entrails through your eyes and use them as reins to ride your soul to hades below!