That's my own rengar build.Hope you guys will enjoy it :)

For every assasin i add 6x crit marks cause , sometimes it helps me when im about to lose 1v1 or fail a cs.

Pros:
+Huge burst
+UNSEEN
+High outplay potential if stacked ferocity
+Strong laning phase
+Easy farm
+Nice set for assasin
+Great gap closer with passive
Cons:
-Risky pick
-Hard to master
-If stunned he's dead

Farming with rengar is really easy , hit your Q to execute minions or W if you want to deal AoE dmg.You can use E to stack your ferocity , when traveling through jungle.

Your main skill is R.It's your chasing/escaping/initiating/soloing tool.Your ult is very easy to counter after last nerf that show offs that you are coming.If you want to initiate a teamfight wait a moment when enemy Mid/ADC will go away from team and kill him.High burst will give u 100% to kill your target , after succesfull kill run away.You dont need to care about chasing u cause of the speed burst after ultimate and Ghostblade.

You are one of the strongest top laners so u can play aggresive.Stack up your ferocity to 5 and walk inside bush.When enemy is going to take minion jump on him or on minion thats next to the enemy.Your combos:
Q->E->Q->W - Lane combo
Stack ferocity to 5->R->Q(while stealthed)->(Q after stealth)->E->W->Q - Early/Mid game kill combo
Stack ferocity to 5->R->Q(stealthed)->Yoummu->Sword of divine->Leap with Q->Q(after stealth)->Hydra->E->W->Q - Late game bursting combo

I think thats all i wanted to tell u guys :) Good luck in bursting enemies down :D