Hello,
i have been playing league of legends for around 4 years - i am Platinum III already. I don't care about my rank; play this game for fun. Play as heros who no have any complication mechanics is boring. I'd like to play as champ who has a lot of ways top play. The best example is the Blind Monk - Lee Sin.
In my opinion, he's the most balanced hero in the League. Every season you can play him on every position and it brings a lot of benifits if you have already known him.

You need to use all his pros to carry your game.

Pros

• Strong early game - has a huge damage and mobility.
• Effective ganks.
• Massive stun when you use good ult.

Cons

• Low scaling.
• Hard to master.
• Sonic wave is the most important your ability - don't miss it.
• Need some practice to use ult effective.

To be honest, the best way to clearing jungle as Lee Sin is start on Krugs. Smite used on Krugs gives you stun every 5th attack. The monk has bonus of attack speed on passive what brings easier killing monsters.

You can watch my video how I clear jungle.

[VIDEO IS UPLOADING]

After this clear you have three options:

• Gank mid lane.
• Gank bot or top lane. (If you are the blue team gank bot etc.)
• Go clear wolves, blue golem and gromp.

Remember: if you don't have enough health go kill crab.

We can take 12/18/0 too, it gives extra damage and armor penetration or bonus 5% CD. But this build does not need that.
Why 12/0/18?
As you know Lee Sin has low scaling stats, that's why we need that key masteries so it's Strengh of ages. It gives bonus for 300 health around 15-20 minutes.
Third three gives us a Tenacity 15% for CC what let us do insec kick easier.
First and third three gives us bonus for shields and life steal. It helps in clearing jungle.