It depends on your setup, and your play style.
I'll explain an old setup that I used.
Armor Penetration Marks x9
Armor Seals x9
Scaling Magic Resistance Glyphs x9
Lifesteal Quintessences x3
21/9 masteries
Make sure that you take hp/5s masteries in defense, as well as the Tough Skin line. This improves your clear and sustain phenomenally. The rest in offense does not matter too much when it comes to clear. Just take the AD line, as well as bonus AD and penetration.
You always start bottom lane, because they can leash you much better than your top laner can leash you. Always get a hard leash to 300 hp, as that is around the time that XP starts to be stolen. This saves you a lot of health early on. Another thing that you may not know is that the small Raptors do more damage collectively than the large one. If you can quickly take them out with an empowered Q and the follow up Q, it can save you on the upwards of 200 health.
These are just small tricks I use to improve my jungling with Rengar. If you have anymore questions, you can respond to this post or add me in game.