He can jungle, he can lane, he can initiate fights, he can chase, he cannot see. He is Lee Sin, the blind monk. Lee Sin excels at almost anything, but he prefers to jungle. Some ask "why jungle?" The answer is simple: with a jungler, 2 summoners can solo a lane which leads to faster leveling and a better early game advantage. With this build, a summoner playing as Lee Sin, the blind monk, can jungle very well and possibly early game gank right out of the jungle for an even greater early game advantage!

Pros

2 solo lanes for early game leveling (due to jungling)
Great support/assassin/dueling capabilities
Fast jungling
Great overall stats
This build can solo Baron (takes long though)

Cons

2 solo lanes might be too much for teammates
Expensive build and not recommended for some who cannot get kills

I chose these items because I have noticed that Lee Sin is very squishy and although his abilities can make up for this, armor seems more reliable (especially for our community's newbies). Although the build is VERY expensive, with a good start and maybe an early game gank, I think you can do it :)

Lee Sin, the blind monk plays very much like Poppy. And with that said, Sheen[*] and Trinity Force[*] are the most important and most useful items while building this character. So right after your Heart of Gold[*] you must buy Sheen as soon as possible! Lee Sin uses very little ability power and so it is not a concern. His abilities (that damage your opponent) are all based on Bonus Attack Damage (I'll call it BAD for short lol)

The BAD items listed give roughly 165 BAD and so with crits, attack speed, abilities+Trinity Force's passive, you should excel in duels and can murder any squishy champion before he can tell his teammates that he is being chased by Lee Sin, the blind monk.

As a jungling supporting ganker assassin with no eyeballs, keeping contact and visuals (even though you're blind) is key to getting quick early kills to pay for this 18,365GP build! If you can play Poppy (the trinity force assassin) well AND play Warwick (the king of the jungle) well then this is the build for you!

Banshee's veil is completely up to you. In fact, I tend to forget about it and buy warmog's armor or simply another bloodthirster. It all depends on how you want to play. Remember that Lee Sin, the blind monk excels at everything and so he can adapt to the items you lay upon him after completing trinity force.

Lee Sin's W skill allows for easy, safe jungling. Besides the shield you get from self casting this skill, activating it again will cause your armor to go up along with gaining life steal and spell vamp. Your E skill is mostly used as a creep killer as it can damage multiple units, also this skill can cripple your targets when activated again. This helps in duels and chasing enemy champions and this skill initially serves it's purpose at rank 1 so I usually don't touch it until i have to.

If possible or comfortable, try to space your ability casts with basic attacks. Lee Sin's passive allows for a minuscule amount of energy depletion and fast attacks (increased by Sheen and Trinity Force). And save your ultimate ability for when you decide you can either get the kill or possibly kick your enemy into another enemy to get multiple kills. (or maybe kick your enemy into the nexus thus winning the game lol inside joke [not really]).

Because you have overpowered and overwhelmed the opposition, your enemies will probably try to surrender or disconnect. But since you are Lee Sin, the blind monk, games do not end and players cannot leave until you say so. Baron might just kill himself as you walk forward due to you being Lee Sin, the blind monk.