PROS
Insane burst
Stun
Can catch runners
Single target instagib
Mapcontrol


CONS
Squishy
Long cooldowns
Not very useful other than slaying single targets.


RUNES
full CDR or full AP/AP@18
With full CDR runes you will have 22,38% CDR at level 1. Combining this with fast Ionian Boots of Lucidity, you will have 37,38 CDR about level 4-6. Allowing you to cast a lot more spells throughout the whole game, instead of slowly adding small amounts of AP.

Evidence:
Sigil of Silence has a cooldown at 6 seconds.
6,00s*(1-0,2238)=4,66s
If we then see how many times we can cast that spell in one minute:
60s/6s=10 times
60s/4,66s=12 times

At level 1 it deals 70 magicdamage, if we add Dorans Ring - it will deal 70+(15*0,60)=79 magic damage. That means 10*79=790 damage in one minute without cdr-runes.
With CDR-runes we will have to extra spells in one minute, 12*79=948 damage in one minute.

Distiortion has a cooldown at 20 seconds before we reach level 8. Lets do the same.
20s*(1-0,2238)=15,52s
60s/20s=3 times
60s/15,52s=3,9~4 times

Etc.

With CDR-runes you will be able to cast Distortion quicker, allowing you to either escape, or engage in fights. LeBlanc is squishy no matter what u do (other than 0/27/3), and you want to deal as much damage as you can - as fast as you can. That's why I like having this sort of flat-setups with leblanc.


My best tip is:

Always rush CDR-boots

Items
Ionian Boots of Lucidity first to almost reach the 40%CDR-cap
Then go for Rabadon's Deathcap
If you happen to die and don't get any kills go with Mejai's Soulstealer and get rabadon's later. Then get Tear of the Godessd to build up your mana for the lategame, and some Sight Ward to prevent you from getting ganked and so you can gank wherever it's neccessary.
Will of the Ancients will let you and your magicdealing teammates have some more survivability because of the spellvamp.

remember to

Place the wards in their jungle!