As far as runes go Lee Sin scales very well pre level 6. So the generic rune build works quite well with him.
The runes are a set of three different stats: Armor, Scaling Magic Resist, and Attack Damage.
The reason for doing Scaling MR is so your early itemization can be more honed into getting your early damage items and your base armor items. Still if the game gets late enough you can't always rely solely on your Scaling MR so be sure to build your MR items along side others :D
Your stats will be pretty stacked in a lot of area's, specifically: Health, Armor, Magic Resist, Movement, and Attack Damage
With how the teams offensive stats stack, being heavy AP or heavy AD your stats will very with your personal preference and what works best to beat the enemy scum ;D

Lee Sin is probably one of the funnest champions to combo abilities on. Not only does it make you incredibly hard to target, but dishes out some good damage and makes for some sweet youtube material plays.
So generally you would start a fight leading with your Q, depending on distance you will either reactive your Q for the jump or save it for either a flash or a dash of some kind.
Following up with your Q you will mash your E twice to get the damage and the slow off as soon as possible, saving your Q also helps with this if the target gets out of range you can reactivate your Q and continue with your slow. This is the generic pre six ganking/trading combo.
At six you basically do the same combo but with some changes if your target is at or around his turret lead in with either a ward jump behind the target or a flash to the same position (Only flash if you know you will secure the kill, and preferably without dying). Once behind enemy lines you will throw your q onto them but as soon as you see that Q hit you ult them out of the turret following up with your reactivation of the Q to bring you right along with him, after which you will mash your E for the slow and continue smashing face, if things get dire no worries locate your team champions or team minions and Safe Guard to safety, if you know you will survive but it will be on the skin of your teeth activate your W twice on yourself to give you a shield and lifesteal to better secure your kill/assist.

Spells to consider taking: A combination of either Flash, Smite or Ignite, Smite. In some cases you can take Exhaust, Smite but those are rare times.

Spells to avoid taking: Spell(s) that are not needed and probably shouldn't picked but can be is Ghost. The rest of the summoners don't even consider taking because heal takes away from your escape or kill security, Clairvoyance is almost useless because if you are really concerned about vision you can buy a blue trinket and still have your escape and/or kill security, Revive is also pretty useless because it has a very long cool down and has a very narrow window of viability in game, Clarity is just stupid, Teleport has a few good qualities but it is essential for either escape and/or Kill security, Barrier is much like heal it will give you added life in a fight but as far as kill security and/or escape their are better options.
Again this is all off personal preference so if you've found a combination that works well more power to ya!

If you can somewhat master Lee Sin you can not only carry your team through ranked victories but can also help your lanes carry you through ranked victories. You'll probably see many Lee Sins being played in ranked because he has so many strong qualities in the jungle and in team assistance.
There is a long and boring argument about how bad a Lee Sin falls off late game, but the way I see it if you've done your job as a jungler you will either, plateau at a very secure stat range, or you will have successfully fed your lanes to the point to where it doesn't matter if you're falling off. But again it is all a game of chance and you will have great teams and then less desirable teams, regardless try with 100% to get to either one of those points.

Pros:
Crazy Mobility
Great pre six trading
Great initiation
Great ability to CC full teams and single one target out and putting him in the full fury of your team
Super stylish play
Cons:
Runs out of Energy quite fast
Considerably squishy at level 1 (only matters if you are caught in an invade)
Has little to no CC break so if you are chain CC'd you have an increased chance of dying without creating a lead in teamfights.

Creeping: Lee Sin has a great Level 2-3 creep clear added with his base stats and his E aoe you can generally clear waves mobs quick, because of this feat you don't usually have to tax your lanes after a gank which is also great for your lanes giving them the chance to max there farm on each minion wave.
Taxing should only happen if, your ally dies in a gank, if the lane is pushed into your turret, or if you are planning on doing something with the enemy turret.
Jungling: Like the paragraph above Lee Sin has great mob clear, this is a very great feat because the faster you can clear through your jungle the faster you can get to your lanes for ganking.
Counter-Jungling: Lee Sin is a great counter jungler because of his inhuman ability to clear mobs and he great trading, though avoid before you are level 4 and have a few items in your bag. You can counter jungle before then if you either see the jungler opposite you on the map, dead, or invading your jungle at the very moment. Other then that avoid it until level 4, once there and your lanes are snowballing feel free to go into the enemy jungle and put him on his toes, no use in sitting around doing nothing if your lanes are winning.

Because of his great mobility ganking on Lee Sin is considerably easier then some junglers, but that is no excuse for stupid moves, you still have to be aware of your surroundings.
Typically the easiest lane to gank is top, because it is a long lane and you can typically successfully gank it with the enemy in mid lane. Unless you are level six or the enemy has used his summoners and/or ultimate or is nearly dead, avoid ganking him at or near his turret, unless your laner is out scaling him or knows you can kill him in a turret dive.
As for the mid lane, it is a bit harder to gank because of its size and access points, most mid laners will ward the bushes directly above and below the lane making bush ganks harder unless the enemy is pushing very hard, but don't fear there is another way! You can successfully gank a mid lane from the upper levels on the outside of the lane near the wraiths and the blue buff entrances, but for this to work you generally have to let the enemy mid laner push to about mid or past lane, unless your laner is out scaling or knows you can kill him, then do your best to get behind the laner and kick him further into your laner/turret.
Lastly, bot, the bane of most junglers existence. Much like any other jungling champion it is a lane you generally avoid unless your team as cleared the wards or the lane is very pushed. But usually that isn't the case, so you have a few access points that can usually result in a kill or two, if your team knows the tri bush is not warded you can come through there and either ward hop and Q to the enemy or Q straight to them if they are near. But luckily for you, you are playing Lee Sin, making it a lot easier to do a bottom bush gank, meaning walking through the back side of the lane and entering its bottom bush, you can continue this gank by either ward hopping behind the enemy and kicking them into your team, allowing them to engage onto your ADC and support, allowing your support to CC one or both the enemy laners, or flashing behind and kicking into your team. Either way you will generally secure a kill in this scenario.

So in summary, you're playing a Lee Sin, you're pulling off some bad *** plays all while being considerably tanky and still dishing out some damage!
I hope you enjoyed my guide and I hope it helped you in your play of Lee Sin.
Being this is my first guide comments and suggestions are great appreciated!
Stay blind my Friend ;D