Hello! Im STRK (Beekz) and i am going to try and help you Learn Lee Sin. I made a guide, but forgot to log in xD this is being written after the guide was finished
Take Flash for the plays, but safety as well. I recommend putting it on your D key.
Take Smite because you are obviously going to jungle with this build.
Choosing Red buff or Blue buff Side
You should probably always start Red Buff side, but if you have a Teemo on the red side or a very bad leasher, you could start Blue Buff side as well.
You should start your gank with your ward hop and your E for the slow and damage. That allows you to have a bigger sticking potential if you save your Q if the enemy tries to run away. If the enemy/ies are fairly pushed up you could try to gank behind them, probably at the tribush way. If you are level 6 you could make a play and kick an enemy towards your teammate/s if you cant gank from the tribush. Lane ganking is also very effective on Lee sin, but make sure you or your teammates have a pink ward so you know that the enemies can't see you.
I preffer to start with a Hunter's Machete and 3 Health Potions and a Warding Totem because when Lee gets his jungling item or a Calfield's Warhammer you don't have trouble clearing.
Try to get money for your boots, a pink ward, and a Calfield's Warhammer/Tracker's knife for your first back. First item should be either Swifties for the map pressure and efficiency, or a Tracker's Knife : Warrior into Lucidity boots later. Your 2nd item should probably be a Hexdrinker or a full Maw of Malmortious against heavy AP comps, or a Black Cleaver if against a more all-rounded teams. 3rd item completely depends on your team, if you already have 2 tanks you can go mire AD focused with 3 tank items, but if you have only 1 tank you should probably build full tank after Cleaver/Maw. Dead Man's Plate is a very good item on Lee Sin because of the HP and Armor you have, and the Movement Speed it offers. Banshees is a very effective item against a team with someone like Blitz/Thresh/Nautilus/Lux...
You have 3 options. The 1st one is 12/0/18, 2nd one is 6/6/18 and the 3rd one is 0/12/18. I like the 6/6/18 one a lot. Flash cooldown is so precious on Lee, as well as Tenacity
I run 9x flat AD Marks, 9x flat Armor Seals, 6x CDR per level and 3x flat Magic Resist Glyphs and flat AD Quintessences. You can swap 1 AD Mark for 1 Crit Chance Mark if you ever need that Crit in your clear.
Easy : Fiddle, Amumu, literally anyone that is pretty weak early on
Medium : Nidalee, Ekko, Shaco, J4, Vi and Kindred at around level 6
Hard : Elise, Yi, Quinn, Shyvana, Udyr, even Nocturne
Champions that Work well with him
Orianna - Ball delivery into enemy team
Morgana - Black Shield for the cc the enemy team has so Lee can do a combo safely
Lux - Shield that absorbs damage
Yasuo - Ult combos with the Knock-up
Alistar - Whoever gets kicked is never getting out
Ekko - W + Lee Sin Basket-roll-ball
J4 - Ult synergy
Braum - Passive
Rammus - Taunt
Easy to Gank targets
Ahri - Pre 6
Nasus - Very very weak early
Vayne - Just like Nasus, just with an escape
Lux/TF - Very immobile
Akali - Lee counters her big time
Draven/Jhin - Very bad early
Xerath - no escapes or mobility
Insec - Q, Q, Ward + W (Ward hop), R
Flashy Insec - Q, Q, R and Flash (Make sure you flash at the right time and position yourself in a way you kick the enemy into your teammate)
Insec + Flashy Insec - Q, Q, Ward hop, R Flash
Drux - Q, Flash or ward hop mid animation, Flash or ward hop to gap close to an Ult range (depends on what you used first), R, Second part od the Q
E + Flash - same as R + Flash just use E instead of R
Q, Flash or ward hop to get in range fir the 2nd part of the Q, Q
Make the most use of the your passive and hit twice in between every abiltty when clearing camps.
Learn to cancel auto animations of monsters in the jungle and walk in between the autos.
Use the 2nd Q as a finisher if you dont need it as a gap closer because it deals more damage the less health the enemy has.
Try to pressure lanes early.
Practise ward hops in custom games and try to find the best keys you can for your wards to make wardhopping easier for you.
Try not to die early on.