General pathing is
Red>>Wolves>>Blue>>Gromp>>scuttle/gank

blue side start:
Blue>>Gromp>>Wolves>>Red>>Scyttle/gank

1. Make sure to always have a ward or two available to hop to with your W, do this with control wards when you can afford them. Don't be afraid to approach a gank with a ward hop if you don't feel confident in hitting a Q.

2. Early game pressure is everything, if you cannot find a gank after scuttle look to invade and ransack the enemy's jungle.

3. It is worth learning how to insec with the practice tool in order to be as effective as possible during ganks.

4. As soon as you have successfully ganked/lose your kill opportunity, look to start framing again in yours or the enemy's jungle. It is improtant to find a good balance between farm and kills.

5. Make sure to be smiting enemies you duel with in order to reduce their damage to you. Don't be afraid to utilise your runes survival capabilities, you can stay in fights as long as you're dealing damage.

6. Make sure to get the early objective such as drakes/tower plates. Make use of your early competetence and map pressure.

7. Later in the game, you will start to fall off; an assassin build can make you more powerful later, however you should look to build someting like steraks, deaths dance or maw of malmortius to keep you alive longer.

8. Have fun! Lee Sin is a difficult champ and requires a lot of practice, so don't feel disheartened when you lose your first games with him or struggle to pull off combos. Just put in the work and you'll improve over time.