The Rengar build for Jungle is Youmuu's Ghostblade and First Strike. This LoL Rengar guide for Jungle at Platinum+ on 13.23 includes runes, items, skill order, and counters.
Rengar Counters
51.1%
(+0.7%)
56.0%
(+0.4%)
3.0%
4.2%
(+0.3%)
713
(+3)