Hi everyone, I'm Cpt Kate, currently in Platinum league and playing in the SEA server. Lee Sin is one of my favorite champion, and he is extremely fun to play due to the outplay potential and mobility. I've been playing Lee Sin since Season 3, and I believe he is one of my better champions. Please take your time to read through this guide and leave a comment for me to improve on :)

Pros:

[*] Extremely mobile
[*] High early game damage
[*] Strong duelist
[*] Able to engage
[*] Strong early game ganks

Cons:

[*] Useless late game
[*] Easily kiteable if you don't land your Q
[*] Inexperienced player may run out of energy while dueling
[*] Ward-jump-kick takes practice to pull it off smoothly

As a Jungler, go with the basic start of Hunter Machete and 4 health pots. After a successful gank, you'll have enough gold for 2 long sword. Buy it without upgrading your machete to spirit stone as the two long sword gives you better combat potential and allow you to snowball into a better duelist. If you can't pull off a successful gank, get a spirit stone instead and continue farming in the jungle. By your 2nd back, you should be able to complete your spirit of elder lizard.

If you have to roam alot, get a tier 2 boot before you complete your sightstone but carry 1 or 2 sightward with you in case you need to ward jump out of a bad situation.

Randuins if enemy AD is fed, or if enemy team have 2 or more champions that does hell lots of damage by auto attack.

Banshee Veil for your MR defensive stats, and if enemy team have lots of CC to lock you down

Maw of Malmortius for better dueling potential against AP mage

Warmog for overall tankiness

At level 1, I'll start off with Q most of the time due to the damage on both cast, and W next for better early sustain in the jungle. Max Q first for better damage.

Now, you have a choice of maxing W or E next.

I max W second because I feel that it is a safer option. It reduces your cooldown on W meaning you can have a ward jump up sooner, as well as the increased shield amount which may save your teammates that's on fire *Ahem ignite*.

Max E second if you want to focus on dueling enemy.

Before you start to learn Lee Sin jungle, you need to have a basic knowledge on what jungling is all about. As a jungle, you'll need to keep this things in mind:

[*] Your role as a jungler is NOT to farm in your jungle all the time unless you're an EXTREMELY farm heavy carry jungler *AHEM YI*
[*] Don't gank a lane because you just happen to be there. If your enemy started the opposite buff camp as you, there's a high chance that the enemy jungler is nearby too.
[*] The best time to gank a lane is when you have vision on your enemy jungler and he is nowhere near.
[*] "If all your lanes are winning, invade the enemy jungler and give them a hard time" - Meteos of Cloud 9

Now, Lee Sin is an EXTREMELY powerful early game ganker. Make the most out of it by constantly looking for openings for a gank and pressure enemy laner. Look for enemy that tend to overextend and gank through the river. If your laner has a decent CC, it'll most probably end up as a kill if you can land your Q.
Because of the strong dueling potential of Lee Sin early game, anticipate enemy ganks and go for a counter-gank. One good way of knowing when will your enemy jungler gank is to think in their shoes. Imagine if you are in the enemy team, and ask yourself which lane are you going to gank. Head over to that lane through the lane and camp in the side bush and wait till the enemy jungler comes.

Basically, try to land your E before throwing your Q. W to a ally or minion to close the gap and E and only throw your Q AFTER your enemy has flashed away. This way, you can have two gap closer which most probably end up as a kill for you as long as you are not in their tower range.

On the note of counter jungling, please consider the strength of your enemy jungler before attempting to counter jungle. Lee Sin may have a hard time fighting against equally strong early game duelist such as Udyr, Olaf, or Elise. This is especially important if your enemy laner is in a position where they can get to the location of the fight before your laner does. However, if the enemy jungler is a farm-focused jungler such as Master Yi, feel free to camp and ward every single camp of theirs to force a rage quit x)

Lee Sin can be either played as an assassin or tank. If played as an assassin, you'll be literally useless in teamfights. Yes, some may argue that the full burst skillset of leesin is more than enough to kill the enemy adc and can still ward jump or flash out to avoid dying. However, the key point to note is that you have to Q in to the enemy ADC in order to burst them. Once you Q in, the enemy team will most likely CC you and you'll be shredded in seconds.

Thus, I believe that a tank Lee Sin will be more useful than an AD Lee Sin in the late game teamfights. Similar to other tank champions, your job in teamfights is either to peel for your carries OR stick to THEIR carries to zone them away from the fight.

Lee Sin can also engage, but this requires a bit of practice. It is commonly known as the "Insec Kick", named after the jungler of Royal Club, inSec. The trick is to Q to your enemy, and then follow up with your second Q and once you're in the face of the enemy, place a ward behind them, ward jump to the ward and R to kick the enemy back to your team.
Harder variations have also surfaced, such as flashing behind your enemy JUST RIGHT AFTER you start the R animation.

However, one keypoint to note is that you should never kick back a tank that does insane amount of CC and disruption, (alistar plz) and on champions that have re-positioning skill such as Lucian or Ezreal E. This is because the moment your ward jump behind them, some players with quick reflexes is able to re-position BEHIND you again, and you will be kicking them away from your team. After that, enjoy being burst down by the enemy team.

That's it for my guide, it is my first ever guide and please leave some comment to tell me the ways I can improve. Thanks for taking your time for reading this guide. I hope this guide helps.