This guide is fairly simple but very effective. All you have to do with Lee sin is spam his spells and heal with your auto attacks. I will explain more indepth later.

The build that is up there you should easily get in every game. The next item you should get after the GA is something situational depending on who's carrying the team. If you have someone like trynd carrying then you are going to want to get a thornmail, If someone like Malz or someone with ap is carrying then you are going to want to get a banshees vial or force of nature. The reason I say to rush the BF sword is because you will have sooooo much damage with your q right off the bat. This will provide you with kills letting you get fed and giving you more damage late game.

Spell spamming is something that you must do often with Lee Sin. For example, to harass you can hit them with your q skill shot fly too them and do a lot of damage then W out before they can damage you. On the slight chance that they do get some damage on you, all you have to do is tap your W again and attack some minions to get some hp back. Be sure to inform your laning partner that you are just harassing with those attacks, often it is mistaken for starting a fight. If you do want to start a battle you q in pop your e twice to slow them then double tap your w to gain health as you auto attack them down. Its fairly simple, be sure if you have your ult to run in front of the person you are focusing (because they are slowed by your E) and ult them back to your teammate. There are so many ways that lee sin gains energy that you should not have a problem spamming them, he gains energy with auto attacks and with his w.

I prefer Exhaust and Flash but another way you could run him is ignite, flash because you have a slow on you E.

If you are playing a 3v3 start out with a doran's blade, if you are in a 5v5 get a long sword and a health pot. Also something cool about lee sin is that if you place a ward on the other side of a wall then you can w through the wall to the ward. also if you can Q someone through the wall you may tap it again to fly through the wall and kick them. Lee sin has many skills and is very effective in both 3v3s and 5v5s. He is very versatile and can jungle easily. All you have to do is pop your w so you can get some life steal and jungle him just like everyone else, but don't take my word for it i don't jungle with him often because he does soo much damage outside of the jungle.