Rengar doesn't play extended fights but instant deletion. The build maximizes initial burst and penetration to ensure kills before reaction.
Long Sword
Sheen proc after saut passive, mana for combo Q-W-E
Lifesteal on Q Savagery burst from invisibility
Anti-heal + crit, burst assassin from bushes or R
Gluttonous Greaves
Stasis
combos burst from the bushes stack Conqueror to fights 1v1 extended.
saut from the bushes (passive Unseen Predator) triggers penetration immediately.
Strengthens autos empowered by the passive Ferocity for a DPS burst increased.
Each kill gank invisible boosts his AD to ambushes increasingly lethal.
Reduces cooldown of the R Thrill of the Hunt to multiplier his assassinations furtifs.