Hi, this is my first guide and its about Lee Sin jungle, one of the best junglers in the game atm. I tried to make this guide as short as i could so you could read it easier and dont mess around with irrelevant stuff.
Lee Sin is a great champ because although he builds defensive items he can deal tons of damage(without a triforce :P ).
Lee Sin has the ability to jump in and out of fights, chasing situations and deal great ganks with his superlative ganking ability.

PROS
Mobility
Utility
Sustain
Never ending energy with Flurry

CONS
Difficulty on mastering
Skillshot player

I am using 7x Greater Mark of Desolation and 2x Greater Mark of Attack Damage which gives a sufficient number of flat armor pen(+15) for jungling. The Marks of Strength are combined with the 3x Greater Quintessence of Attack Damage giving (+8.8) flat attack damage. I am also using 9x Greater Seal of Armor which gives (+12.69) flat armor. Finally, i have 9x Greater Glyph of Scaling Magic Resist which gives (+1.35) magic resist at level 1 , and becomes equal with the flat magic resist glyphs at level 9. At level 18 you have (+24.3) magic resist from the glyphs.
To sum up, at level 1 only from the runes you have

1. armor penetration= +11.9
2. attack damage= +8.7
3. Armor= +12.6
4. Magic resist= +1.35

Masteries

I use the 9,21,0 masteries tree. Regular defensive style jungler giving 9 points to offense aiming to the 10%armor penetration point Weapon Expertise .

Level 1

So at level 1 your champion with the Boots as a starting item has the following stats:

• HP = 566
• Attack Damage = 71
• Armor Pen. = 12|10%
• Lifesteal = 0%
• Attack Speed = 0,68
• Movement Speed = 375
• Armor = 38
• Magic Resist = 38.35

You can start with Boots and 3x Health Potion which i recommend and use for quick ganking and counter-jungling (which i will mention further down) OR you can go Cloth Armor and 5x Health Potion for safer jungling and more sustain at level 1.

Continue with a Madred's Razors and a Doran's Blade for better jungling and more aggresion.
Hint: If your jungle has been ruined or you are back at gold and levels i recommend building 2x Doran's Blade

Finish up ur boots which could be Mercury's Treads or Ninja Tabi (only at specific situations, not much ap on enemy team and no cc)

Also, finish up your Wriggle's Lantern (one of the best items for lee sin)
Hint: ALWAYS carry a ward with you , wriggles provides you one so keep an eye on its cd cause you will use it as an escape/engage mechanism with your Safeguard skill (W).
Hexdrinker is a really good item for mages and now that it can be evolved at Maw of Malmortius i totally recommend it. Now , in situations that your enemy has not a significant magic power you can skip this item.

At this point i kinda stop building offensive items and go defensive. Build an Atmogs Warmog's Armor, Atma's Impaler for great sustain and the passive from atmas and finish up either with Frozen Mallet if u want to be more defensive or a Bloodthirster for more damage if your team has already a tank and you can go as a bruiser at late game.
Hint: If your team has already a tank i recommend getting a B. F. Sword right after Phage

Most people start with Tempest i know but i prefer Safeguard. The reason is that with Safeguard you dont lose so much HP as you would with Tempest. Thats because you get the shield and once you press it again you get iron will which gives you (+5) lifesteal and (+10) armor.
Skill order can change due to jungling and ganking.
Making a quick gang at level 2 you may need to pick for second skill Sonic Wave.
If you are going to continue regular jungling you must pick Tempest at level 2.
I beleive you must keep an equal pace at you skills maxing together Q and W and then E.
Of course level up your R(ult) Dragon's Rage at levels 6,11,16.

APPROVED SUMMONER SPELLS

Flash Smite --> recommended for beginners
Exhaust Smite --> ultimate spells for lee

exhaust is such a strong spell combined with Summoner's Wrath you can burn the enemy ad carry or escape from a chase.
if you are going to use the flash ,smite then change the mastery point and give it to Butcher ,easier jungle.

NOT APPROVED SUMMONER SPELLS

Teleport
Ignite
Ghost
Cleanse
NONE OF THESE ARE GOOD FOR LEE SIN! (you can use some of them but not as jungler!)

Lee Sin is one of the best junglers in the game, he is kinda fast and his ganks are really good.

The jungle route that i recommend is the following:

• If the enemy jungler is starting from blue buff or there is no jungler
  Start with wolves, ask help from your mid to take them down.(DONT LET THEM STEAL ANY)
  Then go to your blue buff and ask mid and/or top lane/bot lane to pull and help you take it down without smite. Then run to the enemy's red buff steal it with smite and leave one minion alive so the enemy jungler will lose exp and gold OR kill all the camp so you get the timer and go to steal it again later.
  Now make sure you secure your lizzard camp (red buff) by warding it or taking it asap.
  
• If the enemy jungler is starting at red buff
  You can do the opposite thing going first at your red buff and then to the enemy's blue buff
  
• If you want you can be defensive and do the regular jungle
  Start from wolves then go to ancient golem (blue buff) use smite then go to wraiths and then back to wolves. Then run to lizzard (red buff) by that time smite will be up.

**When counterjungling make sure you have your smite up for quick counter and also make sure you have a ward and your W not on cooldown so you can escape fast if things get messy.**

** Lee Sin doesnt need blue buff so take the first one for exp and give the other ones to your mid, try taking red buff for ganks its very usefull**

1) The easiest one is shielding your ally. For example, when karthus ult or vlad ult has been casted on an ally you can use your Safeguard at the right time and save your ally.

2)Reaching an enemy champion further away. You can Safeguard at a friendly minion or a ward and then Sonic Wave to the enemy.

3) Using your ult will kick the enemy away. If u want to escape you can aim the enemy near a wall and he will be kicked over.
If you dont want to escape, a good combo would be to mark your enemy with Sonic Wave and then kick him with Dragon's Rage and then Sonic Wave again to catch up on him.

4) If you have found an enemy in a bad position and he is likely to flash over a wall, mark him with your Q and wait till he flashes and then reactivate it so you catch up on him.

5) At team fights you should use your mobility to get around the fight and catch the enemy ad carry. Use your Tempestx2 on him so his attack speed will be reduced.

6) Using your Safeguard twice it will grant you life steal and spell vamp which means that if you use Smite at that time you will gain health. So keep that in mind when ganking you will need it.

7) OMG I AM AT ENEMY JUNGLE AND I HAVE NO WARDS,NO FLASH AND THEY ARE CHASING ME. Chill, Sonic Wave at baron or dragon and you are gone.

8) Dragon's Rage will also kick everyone who is close behind your target so aim well :D

9) Master of facecheck. Just use your Sonic Wave.



Ganking abilities

1) Run at the lane, W on the nearest ally or minion and Sonic Wave to the enemy.

2) Go at the enemy jungle and wait as near as possible to the lane behind a wall.
Wait for the enemy minions to come and when they are near the enemy turret Q on them , wait 1 sec, Q again and you are just behind the enemy.

3) When you are at lane and your team is right behind you but the enemy is running you can slow him and kick him right into your team.
This can be done either with Tempest or with Exhaust or by using Safeguard somewhere in front of him or with Flash

4)At top or bot when the lane is pushed wait at your team bush and tell your allies to back off so the enemy can overextend having warded the river because they think its safe, and then BOOM !


*I understand that you may not be able to understand some of the tactics so i will make a video soon and edit the tactics session.

STRONG AGAINST

If you see Akali on the enemy team just say GG. Akali in order to do damage needs to come near you and her escape mechanism is Twilight Shroud just wait till she uses it and just go in the middle like a sir amd use Tempest and she will get revealed.

For the same reason Lee sin is strong against Shaco, Wukong, Evelynn and Twitch. Just use E when you see them and when they try to go on stealth they will be still visible.

WEAK AGAINST

Generally Lee Sin is weak against champions that have stun effects or snare but a good Lee can escape from any situation with a little bit of luck. But i believe that Lee Sin greatest counters are Trundle with his debuff and his ult and Udyr that damn bear can chase you till the nexus.