Lee sin has strong early level potential use it. The reason why I invade which is most of the time is because he kills junglers so easy when they take damage from big camps. Only go ham when they are half health or you know you can can kill them. If you successfully invade and kill the enemy jungler go to your big camp that you didn't start level 1 and clear it. After you have done that look at the lanes see whats going on. If one of your laners is pushed to the max run to that lane and be patient always be patient in ganks and wait for a opportunity when they over extended to much walk up to him do not Q unless they are low for a kill. walk up and E activate E again for slow and auto attack to apply red buff,if they flash that is when you Q and try to get the kill if not it's fine as long as you burn flash its a successful gank. Always Always come back when they burn flash, you have to pressure them and make them suffer until they flash again. Don't focus to much on ganking, farm jungle also and protect your buffs then come back and own lanes stay ahead and dominate early and mid game.

Lee sin loses alot of his potential in damage unless you get fed you still do alot and remain tanky. If they have assassins (Zed,Talon,Akali etc.) protect your adc and peel,always W when you know to and save kick for the adc so the assassins are not near. Do not try to be Insec or TSM amazing and go ham and try to be flashy and die then lose the game. Be smart and play smart.