Always take flash (Unless you main Shyvana / Nocturne and can use exh / smite and have experience with it,) there is no exception to this if you decide to take duo offensive spells - You will be in for a rude awakening. In lower elo, you may be able to do this and that would be 1300 and below, doing this in any elo higher than that will compromise your ability to do anything.  Kha'zix is weak against hard cc and aoe team comps early on and his ulti does not protect him until later on with evolution points.  You will need flash to escape such a sticky situation because it is assumed that no kha'zix is just going to walk up to people to gank them, but use his E to close the gap, therefore, limiting his escape abilities until level 6/11.

Take when jungling to help clear creeps faster and take over global objectives and push for ganks faster.  Take on 3's if your team doesn't have one and for all other situation's will suite them. The rest of the summoner spells are ineffective on Kha'zix.

Kha'zix has strong potential to gank early and invade because of his passive that proc's a very potent slow followed by a devastating isolation target Q.

To easily gank a lane, wait in a bush till an enemy unit is over extended, use your E to gap close the distance, land a basic attack first, do not push Q first then auto attack [Q does not proct Kha'zix slow], they will escape / flash away before you can actually kill them.  Whereas, if they had a slow attached to them you could still potentially catch up to them even if they flash away.

Note that if they do flash away you've created an opportunity for the lane and you've applied pressure to the lane and your gank was successful.  Don't go running back in and getting yourself killed trying to kill them and costing your life.  Remember that dying as a jungler early on will cripple you and depending on how good the enemy jungler is, would or can possibly severely cripple you.

Runes are often situational but I find these to be the most effective, of course if you feel they are a tanky team of enemies you may want to go for armor penetration reds/marks instead of flat damage.  That would be the only substitutionfor Kha'zix rune set.

Reason behind this is, Kha'zix is really good with early game damage since he's an assassin, but he's also very squishy to remedy this I take HP in masteries with some resistance as well, and armor/magic resist runes to help keep him slightly tankier than he would be with other runes.

Flat AD Marks – To get early game damage and help clear in the jungle with some nice Q damage for early ganks

Flat Armor seals – To help you get safely through the jungle and not get executed and also helps for ganks against bruisers and bot lane

Flat magic resist / Scaling magic resist – Know the difference between the two one is more effective for early ganks when fighting magic damage (mid/jungle ap) the other is more effective if you are looking to be a tank into late game I take flat magic res because I don’t intend on dragging the game beyond the 35 minute mark game as Kha’zix you start to scale like shit after that point and it’s best to just end the game quicker rather than later. Don't confuse falling off with being totally useless but rather being gimped in your ability to perform at your most optimal point unless you're like really fed, Kha'zix is an assassin as all assassin's they fall off think of him like talon / lb if they never fell off and became like range carries late game holy hell would the game be broken.

Flat AD Quints – These quints no matter what role you are playing must always be AD the only ones you can swap out are the marks because having flat AD helps in last hitting but for jungles it’s just a damage boost so that is why only marks get swapped in this build (without ad you'll clear slower then shen jungle)