In this guide, I will show you how to cockroach, and I mean how to play Kha'Zix like a like an irritating bug :D
Kha'Zix is probably the best Assassin in my list of assassins, as Kha'Zix has a lot of mobility, DPB (Damage per Second) and sustainability.
Kha'Zix is a durable champion in both Jungle, Top and Midlane, as of the recent meta's. Kha'Zix is able to execute and chase champions as quick as he can, as his available abilities allow him to execute and chase. This guide will specifically guide you on how to Jungle Kha'Zix.
Good Huntin'

These are the runes I use when I play Kha'Zix. Taking armor pen. will give you an advantage as they affect jungle minions aswell.

Passive - Unseen Threat
When Kha'Zix is not visible to the enemy team, he gains Unseen Threat. Unseen Threat lasts until consumed and has no internal cooldown.
Unseen Threat causes his next basic attack against an enemy champion to deal 「 15 - 190 」 (10 + 5 / 10 / 15 / 10 at each level) 」 (+ 50% AP) bonus magic damage and Slow by 25% for 2 seconds.

Q - Taste Their Fear
PASSIVE: Kha'Zix passively marks enemies that are isolated from their allies. Enemy champions are marked as isolated when they have no allies
ACTIVE: Kha'Zix slashes the target enemy, dealing physical damage. Isolated targets receive 30% extra damage.

Evolved Enlarged Claws - Increases the range of both Taste Their and Kha'Zix's basic attacks by 50-units. Additionally Taste The Fear deals extra damage to isolated targets, and base damage in general.

- As these statistics say, Q is a relatively useful skill to evolve first, as it gives you boosts to attack damage, range and isolation damage.

W - Void Spike
ACTIVE: Kha'Zix fires a cluster of spikes in a straight line skill shot which detonates on the first enemy struck, dealing physical damage and slowing enemies. Monsters receive 20%
extra damage.

Evolved Spike Racks - Enhances Void Spike to fire three spikes in a cone, increases the slow to 50% and grants vision of champions hit for 2 seconds. Multiple explosions upon the same enemy do not deal extra damage, and the vision does not apply to stealthed units. Being within multiple explosions does not heal Kha'Zix for an extra amount.

E - Leap
ACTIVE: Kha'Zix leaps to the target location, dealing physical damage to nearby enemies upon landing.

Evolved Wings - Increases Leap's range by 300 (900 total range), and causes kills and assists scored by Kha'Zix to refresh Leap's cooldown.

- Leap would be a relatively useful skill to upgrade second, as it gives you plenty of mobility and resets

R - Void Assault
PASSIVE: Each rank of Void Assault allows Kha'Zix to evolve one of his abilities, granting it an additional effect.
ACTIVE: Kha'Zix enters stealth for 1 second, acquiring Unseen Threat.png Unseen Threat, gaining 40% bonus movement speed and ignoring unit collision while stealthed. After leaving stealth for 2 seconds, Void Assault can be cast a second time within 15 seconds at no cost.

Evolved Active Camoflage - Allows Void Assault.png Void Assault to be cast up to three times and the stealth duration is increased by 1 second (total 2 seconds).