You do NOT need that much armor pen on Rengar. Unless you're playing him top lane you shouldn't be taking armor pen at all, especially not quints.
On rengar you should be taking one of two pages:
Attack speed quints with AD reds
AD Quints and AD reds
Glyphs should almost always be CDR or CDR/Level.
Seals should be armor of course.
Rengar is like WW. Hit 6 as soon as possible and then gank with your ult. Unless a low mobility lane bully like Darius etc is super overextended then ganking will have little success.
Rengar is overshadowed by tank junglers, so he's not played that often in the jungle by pro players. I don't really watch guides, just streams,you can watch vods of streams on youtube, here are some high elo rengar players: Crumbzz, Avaiil, Ryan Choi just a few I know. Use probuilds for some ideas for builds but Rengar's build is pretty binary.
You can keep looking to pick someone out alone, get vision control of their jungle deep wards etc, or you can split push, build tankier, or force objectives like Baron drag and towers. Most important thing is vision control here.
AD and Attack speed runes are important so you can clear quickly and get to 6 quickly so you can impact the game more quickly. It's all about clear efficiency and with Armor pen runes like you have it takes too long for the runes to pay off.
It really is situational. If you need to be making plays all around the map go mobi boots, if you are just looking to have your ult on a low CD lucidity boots.
If you are using attack speed and ad reds with CDR glyphs and managing your skills efficiently, you should be able to do a FULL clear of your whole jungle on your first clear with 2 pots. Remember to smite krugs/gromp and your second buff, while kiting your camps as well.
Build should almost always be Warrior>Tiamat>Ghostblade>LW with lucidity boots/mobis somewhere in between. Can either go for more damage afterwards with a TF/IE or go more tanky with a GA/Banshees/Randuins etc. Just PLEASE do not be that guy that builds the same thing every game because it is necessary to adapt your builds to the situation.