Considering this is my first time making a build on this site lets see how it goes. I know this build is a bit off from some lee sin builds but this is how I play him. Mind you this isn't a set in stone build, it tends to differ depending on what the other teams composition consists of.

So the attack speed glyphs.. I know some people are going to hate me for using them but I find them very useful in the jungle. They allow me to clear at a faster pace early on and allow me to gank FAR more frequently.

As for the other runes, they are pretty standard for junglers, armour seals for less damage from neutral mobs, flat attack damage marks (just for the damage of course..), and armour pen. quints for the ganks.

Short and sweet right?

OKAY, this is where I have strayed away from most other builds, YES I know I didn't put a point in executioner, the reason being is because when you gank a lane you want the laner to get the kill over you because you want to feed your carries. Also, the points in "Havoc" help your damage output Immensely during late game. Since I took the points out of the offense tree you have 2 options:

1. you can do what I have listed above in the defensive tree and put points into basic armour and Bladed Armour. Bladed armour is VERY useful in your early jungle, the pesky little monsters that normaly take u 3 hits to kill now only take 2! This is HUGE, your jungle should be much easier and a LOT faster (my first time doing this I started at red, and the jungle went SO fast that my smite wasn't ready when I got to blue buff and I had to kill it without smite O_O).

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2. You can put points into the support tree and take the improved buff duration with health regen. To me this isn't QUITE as good as the bladed armour because the jungle takes longer to clear and you only NEED the red buff, the blue buff isn't THAT important to lee sin, so the buff duration would only be helping one thing anyway when the bladed armour allows you to gank a TON more.

Pretty standard Fighter/Bruiser items, (IMO) you should get wriggles first before boots (merc treds) if u cant get them both immediately after ganking lanes. This is because if you get thewriggles first you have more damage and lifesteal for killing champions rather than clearing the jungle faster with boots, and you should be clearing it faster anyway with wriggles because of its passive proc. Phage is pretty much a MUST on lee sin jungle, just because it builds into a frozen mallet which GREATLY helps you in team fights Mid/Late game, Tri-Force because lee sin uses all of its stats given and its an all around good item (BUT if you are the jungle lee sin that is forced to "TANK" for the team replace this with a defensive item like FORCE OF NATURE or RANDUINS OMEN ). If the game gets to hyper late game, you should start thinking about buying an INFINITY EDGE just for the damage really.. (IMO) you should never sell your wriggles lantern as a lee sin because it allows you to get out of sticky situations really easily (just plop a ward and u get to trololol the other team)

RIGHT... so im going to make this really short and sweet.

-Get your "E" first for the AOE damage for clearing mobs faster and make sure u PACE yourself when doing your skill sequence to activate your passive more efficiently. (You should max this 2nd!) <

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-Then get your "W" for the shield and the life steal. Again, make sure you pace yourself with 2 skills now (you should be able to sustain your passive if you're REALLY experienced). (MAX THIS LAST PLEASE PLEASE PLEASE)

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-Then your 3rd skill you get is your "Q". Use this to get to your mob camps quickly and clear up pesky mobs that don't die when you run away from them -_-. This is your ganking skill... you should be level 3 by the end of your jungle clear so right when u get this GO GANK, you can use this to quickly get to the enemy laner by hitting him with it and dashing in, OR you and run in and E them slow them down and Q to catch them if they flash away.
(MAX THIS FIRST)

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-And of course get your Ult whenever you can...

-If you took improved smite in the defensive tree then you get 10 gold every time smite is up... pretty simple.. And for all you people out there who think the jungler doesn't have to take smite... you are WRONG. Smite is not only used to clear the jungle FASTER but it is also used to SECURE baron and dragon. It is imperative that you use smite to kill these 2 bosses, unless you want baron and dragon stolen from you... TAKE SMITE.
-Exhaust is a good skill to take as the jungler, primarily for ganking lanes for the slow, but also to get away from deadly counter junglers if they so happen to be strollin on by.
(you can also take ghost for speed, cleanse for a tank role, or flash... because flash is flash) although if you have a wriggles you can just use that as your "flash".

ALL AROUND...
This probably isn't the BEST build out there but I do know when I myself do this correctly I tend to get very good KDR and my teamates normally share in on the kills. Unless they screw up during ganks and I have to pick up the kill... then all is well in the world.
_NOTE: As lee sin... you should NOT carry the game... get that mind set out of your brain right now! your job is to get kills for your team mates, and control the Buff distribution among your team. SINCE YOU DO NOT USE MANA... GIVE 2ND+ BLUE TO AP CARRY >_<. Ward dragon and baron when you can, if you can't let your support know.

_Pros:
-He is Lee sin... The blind monk...
-Tanky with a lot of damage.
-Clear the jungle VERY quickly.
-Ganking is EASY
-You don't die off late game
_Cons:
-If not done to Perfection/Near perfection you may be drained of cash...
-You rely heavily on early ganks and need the assist money.

For the route I normally take: (with bladed armour)
-Start at RED
-Then go to wraiths (use your "w" to lower their health evenly, then "E" to kill them all instantly) <--- kills them faster.
-Next go to wolves, hit the big one 3 times with "W" and passive then "E" to lower them and finish by hitting wolves twice. (bladed armour reduces the amount of times u have to hit them, making this process faster along with wraiths)
-Then BLUE, you DO need the first blue... you need the experience from it to go gank.
-If lanes are not ready to be ganked go back to wraiths and clear them again.
-If lanes are STILL not ready to be ganked go to golems and let your team know that you're ready to gank and they should let lanes push in.

IN TEAM FIGHTS:
_Initiate by AOE "E" followed by the slow.
Step 1: Find your way to the ranged carry...
Step 2: Dragon Kick the ranged carry into your team so He/She is easier to get to.
_Note: if the ranged carry is not the biggest threat (Ex. A Xin Zhao beating up your team Use your dragon kick to Keep him away from your carries...)
_Note#2: TRY TO DRAGON KICK THE ENEMY PLAYER INTO THE OTHER PLAYERS! this helps the team a lot in the sense that u have made the enemy useless to each other for 1-2 seconds.
Step 3: Continue the burst/sustained damage and do your best to keep damage away from the carries.
Step 4: If you are the last one alive, and you think you can handle clean up, go for it.. lee sin is very effective in cleaning up fights, the AOE and the chase mechanics that he has makes for very easy chase...

SOME COMBOS/TIPS:
1. When covering for a lane (someone has backed and they need someone to protect tower) and you can't manage to get into melle range to harass or get last hits on minions, you can "Q" dive in and get the last hit/ damage on the champion and then IMMEDIATELY "W" to the furthest minion that you can to get out safe. (this makes for great harass and allows the laner you are covering for to come back to an easier lane process).
2. FOR HUGE DAMAGE IN 1v1 confrontations:
Q,R,Q,E. It's pretty freaking amazing...
Watch this guy do it perfectly and you will see what I mean
3. Buy a wriggles... save your life... plop a ward down over a wall and "W" to it to get away from nasty situations.