Hi everyone and welcome to my Lee sin guide, i hope you like it and get it to work for you.
This is my first guide and id appreciate any feedback good or bad :)

Few quick things about Lee:

1. He is not a Carry
2. He is not a Tank
3. Although his Ultimate has absoloutely immense damage it really should not be used to killsteal or last hit a champion unless you are absoloutely certain that it will kill them and there is no other way they are going to die as it will save them if it fails.
4. Can solo baron with my Core build (inc the dorans blades)

Going to do this section first as its probably what most people are going to come and look at.

First thing you want to start out with is a dorans blade, Damage Hp and lifesteal, whats not to like.

Next you want to work on your boots, ideally when you go back level 1 boots and another dorans or if you are doing well and know how the game is going to progress level 2 boots and dorans.

From here you want to work on your Bilgewater cutlass and after that Phage and Frozen mallet, from there Atma's and then finally finish your core by making your Cutlass into a gunblade for the increased Ad, Ap, Ls, Sv and the increased range on the slow.

This is your core item build but as with any champion in any game you must change accordingly, if you find you are up against to many Ap, get a Hexdrinker and Merc Treads, Balanced team get Swiftness and if you think its gna be a quick game get Zerkers.

When you finish your Core build you will have the following.

2xDorans
Boots depending on game
Hextech Gunblade
Frozen Mallet
Atma's Impaler

Obviously you should change the 2 Dorans according to the game to Bloodthirster/Banshee/Black Cleaver/Hexdrinker/Infinity Edge/Last Whisper according to the game but it really should be over by the time you farm out the 11180 gold for the core build :)

I Do not think that sheen is a good item to put into this build and the reason for this is because you need some form of defense to survive team fights and nukes, frozen mallet and atma's provide this, having trinity aswell would be to much of a waste imo, maybe replace 1 of the dorans with sheen if you really wanted but i still dont see how its worth wasting 100 hp, 12 damage and 3% lifesteal on at least till you have a decent amount of AD, which you wont have very early.

Pro's
Amazing Team player
Crazy Damage
Super Mobile
Can Jungle
Ridiculously powerful 1v1

Con's
Squishy if not build slightly defensively
Item Dependant
Focused very hard
Ulti can be devastatingly bad if used wrong (With jarvan's ulti for example)

Runes are very simple for Lee, Armor pen marks and Quints, Attack speed seals (can also be Armor and Hp per level) and Ap per level glyphs or attack speed.

Before the panic of zomg AP on Lee ! ! !

There is a reason for this, Lee's W works with AP, now if you look at the options from glyphs really there isint much thats super beneficial, lee doesnt work very well with Cdr as his spells are on low cd's anyway and he should never have the blue buff, he isint an auto attack hero so no point getting attack speed really and magic resist well you arent exactly fragile when built like this.

Your team will very much appreciate having a more powerful shield for team fights and also you get Ap from 3 sources when you build the same as i do, Masteries, Gunblade and Glyphs which give a nice little chunk all through the gamw without ever building for it.

I play 15/15 on Lee, ill go through the lines 1 by 1 so its easy to find why i take each point

Offense:
Line 1. Crit vs ap, both ok but not exceptional, take whichever you feel like :)

Line 2. Attack speed vs Cdr, imo Attack speed is best here as Cdr really isint worth anything on lee he always has something to keep his passive going but none of the 2 are super beneficial really.

Line 3. Armor pen is self explanatory and minion damage works well with tempest and last hitting.

Line 4. + Damage is self explanatory.

Utility

Will be updated later, changed from defence tree for max xp / increased duration of buffs and movement speed

Passive. Flurry - 50% attack speed increase for 2 attacks and 15 energy refunded each after spell cast.

Q. Sonic Wave/Resonating Strike - Skill shot scales with AD/Teleport to unit hit by Sonic wave, scales with AD, does damage equal to 10% of the targets missing hp at all ranks.

W. Safegaurd/Iron will - Shield that scales with AP, can be cast on ally for free teleport or self cast/Lifesteal armor and spellvamp for a few seconds.

E. Tempest/Cripple - Aoe Nuke/Slows hit units attack and move speeds, Scales with AD.

R. Dragons Rage - Amazing damage kick, knocks primary target back and all units hit by primary up in the air.

Lee's abilities are very powerful but to utilize them correctly you absoloutely have to use his passive, which means Q, attack, attack, Q, attack attack, W, attack attack, W, etc.

While leveling i mainly skill W then E then Q last and ofc ulti where i can this is because the shield is actually very powerful during early to mid game and you get the 10% missing hp at all ranks on Q and the slow is increased on the higher ranks of E.

Exhaust and Flash Both for position of my ulti and espcaing mainly, Ghost is a possibility here aswell but i feel it is the weakest of all the options, landing your ulti correctly will either make your team love or hate you so i feel this is important.

If you are serious about playing well with lee sin you will find yourself reading this section.

This is where Lee thrives, he is amazing 1v1 but in the middle of team fights not being the main threat or being the tank.

You bring 4 main things to a team fight.

1. Amazing Aoe slow
2. Awesome damage
3. Ability to cc most of there team with your ulti (and do a lot of damage to)
4. Safegaurd, i cant praise this spell enough, honestly its better than janna's shield because it moves you next to the target and you get free lifesteal and armor after you use it.

When a Team fight breaks out, your role should be covering the sides and back, proctecting your carries, you should not be on the front line with your tank, wait for them to initiate and then you can jump to them, get your shield broken for free energy and aoe slow with cripple, flash ahead of the team, kick someone back and knock the enemy team into the air, exhaust on 1 of there deadlier heroes and chase down with resonating and cripple :)

(perfect example, probably not going to happen very much but we can all dream)

Obviously that sort of circumstance doesnt happen very often but when poking as a tema fight is beginning, you can be on the other side of the walls using sonic wave, or shielding allies, there is always something useful you can be doing :)

Creeping is simple enough, last hit as much as possible keep your passive up and from level 3-4 get into the jungle as much as possible safegaurd and iron will are god sends in there, most of the time you can come out at higher hp than you entered.

Skill Uses:

1. Kicking the tank through the team to knock them all up
2. Saving an ally who is being chased
3. Interrupting channeling spells
4. Getting 1v1 with someone(kick over a wall) flash of resonating after them
5. (cant believe im putting this here) Last hitting champions, really, do this with extreme caution please it really shouldnt be used for this but it is quite effective if you have a lot of AD.

All in all id say lee is an incredibly fun champion to play but he has a very harsh learning curve and you can feel like the weak link on your team if you dont do well early on so dont let that happen! stick with your team and stick to your role.

Hope you all enjoyed my guide please dont downvote unless you have a good reason, if so let me hear it to please :)