I just wanna let you guys know that this is not the RIGHT build by any means and u can feel free to change it as you like. Basically what i did was think about my difficulties with Lee Sin with my early game, sustain, late game etc. and solve thoose problems with my items, masteries, runes and skill order. Therefore i may not be solving your particular difficulties but still, it is worth it a try :D

Ok, so firstable, about my masteries and why would i pick them: in the offense tree, you have several options witch should reflect on your play style, so i use the Cooldown reduction to allow me to catch up a gank even if I miss on my 1st attempt. Now some of you might be asking why wouldnt i get a 21/9/0 build (like an off tank)
So basiclly Lee Sin doesnt really need the masteries on the defense tree because of his health per level stats wicth will cover up moslty all of your defensive needs until you get your Frozen Mallet
My Runes for Lee Sin sre pretty much standard for a melee dps, but, even though you dont need them, you may also take more defensive runes, for example: Dodge seals Greater Seal of Evasion Armor Marks Greater Mark of Armor Magic Resist Glyphs Greater Glyph of ArmorIf you do Prefer this Setup, make sure to get Nimbleness in the defense tree as well as Resistance .

Jungle Build:

Starting Items: Cloth Armor + 5x Health Potion or Vampiric Scepter
Early Game: Boots Wriggle's Lantern Phage
Core Items: Frozen Mallet Atma's Impaler Mercury's Treads
Late Game: Warmog's Armor Bloodthirster Infinity Edge or Last Whisper

For your jungling build, as long as you build up to Wriggle's Lantern, you may start with Cloth Armor and 5 Health Potion or just a Vampiric Scepter. Both will give you a lot of sustain in the jungle.
Your first investiments are Phage and Atma's Impaler your boots dont need to be upgraded yet ( in case you had a bad early game ), the slow from Phage and Exhaust should let you gank anyone.
Finally your late game items must have Warmog's Armor for massive Hp and a good chunk of dmg from Atma's Impaler. At this point, you have 2 options:

If you are carrying the team:

Bloodthirster and Infinity Edge ( if your enemies have a lot of hp but not that much armor ) or dish Infinity Edge and get Last Whisper ( if your enemies's roll is armor )

If you are not a big source of dmg and cant get many kills for your team:

Force of Nature and Banshee's Veil theese two items are very important if u cant burst your enemies down because you dont have any means to protect yourself against mages or AP in general, making the best choice for you to be Magic Resistance.

Lane Build:

Ok, Before the build setup you need to know my laning build objectives:

Great Sustain
Strong Harrass
Lane Domination

Alright so here is my build and why did I choose it that way:

Starting Items: Boots + 3x Health Potion
Early Game: The Brutalizer Mercury's Treads Phage
Core Items: Atma's Impaler Warmog's Armor Trinity Force
Late Game: Force of Nature Bloodthirster

Alright, the Boots and Health Potion are of course the best idea for a laning Lee Sin because of the sustain that he needs and the speed advantage. That way you can harrass your opponent and evade Damage.
My early game purpose is be able to harrass my enemies enough to force them to recall, and push the tower as fast as I can, so, the slow and HP from Phage and the tenacity form Mercury's Treads will cover my defense needs in lane.
My core Items will give me alot of consistant Damage with Atma's Impaler + Warmog's Armor and also a good burst Damage with Trinity Force
The late game items should be a reflection of your enemy team countering them with armor or magic resist and getting Bloodthirster at the end.

Yes there are alot of jungle routes for Lee Sin but I use ans especific route so I can use my strongest gameplay: Low LVL ganks.

Jungle / Ganks route:

1.

Double golems: call for a leash and save your Smite

2.

Lizard ( Red Buff ): Learn Tempest and Smite him

3

Wraiths

4.

Gank ( Mid or Bot while on blue team OR Mid or Top whille on purple team )

5.

Wolves

6.

Give your Mid teamate the Ancient Golem ( Blue Buff )

7.

B and get your Madred's Razors and Boots


Now it is up to you, clean up your jungle, look for pushed lanes for easy ganks, cover a lane if necessary, push a tower if requested, and always remember: the jungler is a team player so dont get greedy for kills and keep your comunication with your team goin!