Having been in the lower Elo's myself, now playing with fellows at higher Elo's rage is a big thing.
As a jungler your job is to help lanes carry, further leading to Victory at the end of the game.
Yes sometimes it seems like its Undying Rage (pun intended) but you have to be able to ignore the players throwing the hate your way.
Just hit the ignore button, and move on to secure the next kill.
It's the key to getting better.

If you have played Kha'Zix before, you probably know that he is almost annoyingly weak in the early stages of the game. Due to that, the Hunter's Machete is the best item to start with in the jungle. Its passive

Starting Items:
Arguably, the Dorans Blade isn't the best item to get when you are a jungler.
I honestly (when jungling traditional junglers like Sejuani or Udyr) prefer to go with the Hunters Machete and 5 Health Pots, but I have been trying out many builds and I found that the Dorans Blade is a perfect fit for the purpose of this build (a Hyper Carry) (given that I would just eventually never upgrade and end up selling the Machete later on in the game).
Even though the item has received quite a significant nerf, it still is good enough to suffice for this build.


Must Have:
Agreed, these items honestly, on paper, look pretty pathetic.
I've spent a lot of time trying out different items and I've found that these items seemed extremely core to being able to Hyper Hyper Carry.
The Hydra worked extremely well when I would combo it with my Q and AA's.
Auto+Q+Auto+Hydra dealt a lot of damage in under 2 seconds.
The BT is a must for it's OP Passive. It gives you +100 AD (Full Stacks) and almost 20% LS... OP!
The Zephyr was a great item, especially if you choose AS Boots. It gives you Great Attack Speed, good Movement Speed, and a decent amount of AD, but it does lack there a little. Still a pretty core item for the much needed DPS!
Now for boots...You can (if you prefer) get the CDR Boots if you so please. I only chose the AS Boots because I found they worked well if you got them right after the Hydra.
It is a preference though! Although I would recommend AS Boots if you're still even slightly new to Kha'Zix.

Situational:
These are quite a bit of items to have to consider, but they are honestly all situational. Never once did I seem to need any one of these items all the time.
I will admit that you will probably almost always want the PD or Statik because of the Crit Damage it gives PLUS the Attack Speed, but even still. Choosing between those two items I found were entirely situational.
If you're up against tanks.. take the Last Whisper. If they have really tanky champions, take the Black Cleaver as well (and so on and so forth).
The Manamune, honestly, was pretty nice to have in my build, given that it allowed me to solo Baron Nashor with a close to full build while the item was Active.

Trinkets:
Take whatever you want for a trinket. :)
I choose the Warding trinket because it allows me to ward a lane that I've recently ganked to scout a counter gank.
Trinkets are all about Preference!

You should almost always take Smite. You have no reason not to.
Kha'Zix is way too weak early on to not have Smite.
Flash is also a must have. His Leap (E) is too long of a cooldown, so if you use it and instantly regret going in, you'd need a good flash to get you to safety.
You can also run Ignite instead of Flash if you wish, but I would only recommend that to the more confident players.

Your Q is a MUST for Level 1.
You should try to max it first as FAST as you can! It's the main damage dealer you have and can be combed extremely well to deal Maximum Damage along with you autos and the Hydra's Passive. (Auto-Q-Auto-Hydra Active over and over and over)
Your W is the next priority as it helps slow champions that you gank or it can be used to secure the kill that you're just out of reach to secure.
Your E, the Leap, shouldn't ever be maxed early.
I don't know why anyone would honestly, due to it's long Cool Down and lack of damage. It should be used primarily to initiate a gank or fight, or to close in on or secure kills.

EVOLUTIONS;

First:
Evolve your Q. It gives you a significant bit of extra range and damage which makes successful ganks easier.

Second:
Evolve your E. It is SO important to evolve your E right after Q. It gives you a much bigger Leap range to either jump on fleeing champions, or get away from that team fight gone wrong much easier.

Third:
Unless 'The Hunt Is On' you should figure out which you need more. The extra Ult cast for the speed and Invisibility, or do you need the extra slow from your W? This fink evolution is entirely situational, but I would recommend your W because of the crazy slow, and range of the shots it gives.

This is pretty basic.
Get 23 in offence as shown so that you can output as much damage on target champion as possible.
I have the 7 points in Defense just to give me the survivability I need that Kha'Zix tends to lack.
I got the Health Regen because he is so crazy weak until his 6, that he needs as much Health Regen as he can get. The Dorans blade cuts away from the extra Damage he could be doing to the creeps, but it gives him a little bit of health, some "Life Steal" and a little bit of damage, which isn't a bad thing at all.
Anyway, I also took the increased MR and AR because you should have some when banking lanes, otherwise you may have a chance of being eaten alive before you can give it a fighting chance. That little bit of MR or AR could save you from that one hit that could have killed you.
Also take the Vet. Scars for that extra health, which is quite nice to have.
You don't need anything really in utility, unless you wanted the 3 points in Movement or Mana Regen, which is understandable, but you shouldn't really need the MS because of your ulti, and you don't need the mana regen that badly, because unless your Mid is crazy mana hungry, you should be able to pick up a couple blues to sustain your mana for the earlier stages of the game.

What I found to be very effective was to get a hard leash on blue.
Thanks to the new CD on Smite I can Smite it for a faster clear.

Head straight to red. I find that you get there earlier than the CD will allow you to start so I wait until the CD of Smite reaches between 5-10 seconds then start red. Be sure you aren't getting counter jungled. That can suck!

After that (depending on your health) do as many other minor camps you can to get you some levels and Gold.

Eventually you WILL need to back pretty early, but that's ok. Just see where the enemy jungler is and that'll give you a good Mental Image of what you should do next.
Anyway, you should probably buy a Long Sword and some Pots. This will give you greater damage and survivability in the jungle, helping you get to level 6.

Once you hit 6, start ganking a LOT. But never over commit! That can be very risky if you're not focused and confident in your skills

This build will only do well if you can carry your team!
If you do not help them at all, you're just a very squishy target with no team to back you up!
Remember to Gank any and every lane! Especially the ones that are losing! And help them PUSH!
Remember what (and all credit to) Trick2G says! "TAX THE LANE"! If no one is there opposing you.. PUSH IT! If your team-mate is losing lane, gank his lane and help him push back!
You're the strength of your team! And that strength CANNOT be 'unleashed' unless you HELP THEM OUT!

Thank you for reading my guide!
It's my first one so it obviously will have it's kinks and stuff.
Any constructive criticism will be accepted :D

Just remember!
You're only as good as the team you help out!