The Rengar build for Jungle is Youmuu's Ghostblade and First Strike. This LoL Rengar guide for Jungle at Platinum+ on 13.24 includes runes, items, skill order, and counters.
Rengar Counters
49.7%
(+2.3%)
53.2%
(+0.8%)
3.1%
(+0.2%)
4.4%
(-0.8%)
717
(+61)