Not really a guide, I wrote this for me to test some stuff..

Decieving Lady LeBlanc is really fun to play if you get used to her ;D

Seriously!
Despite the fact that many don't like her endgame and teamfight abilities, I advise to try her at least once with this build.
Not only can you poke them in the eye - you can snare them and hunt them down like rats.
Ok, and you can smash them like rats ;D

I strongly believe that people just underestimate her snares and mobility along with her short cooldowns.

If you disagree with me please tell me so and help me getting the crack of her ;D
But I feel like understanding her quite well ;P

Please note that this is my own and free opinion - no reason to vote down just like that.
Give good reasons for doing so. Would help me alot!

Pros

Good nuker
Good chaser
Easy ganks
Easy escapes
Low cooldowns
Ultimate on rank 3 doesn't cost any mana
Can slow, root and silence for good periods of time


Cons

Moderate or hard to master
If you miss Q you are likely to spam wrong ultimate spells ;P
Bad endgame scaling
Instantly dead if snared

Builds

Build 1 is a reliable build with early good AP and mana regeneration and late game sustain but less cooldown reduction and late game poking ability then my second build. But with blue buff your cooldown reduction should be around 39%, though. It also happens to be my favourite :)
Try it out, it's easy to achieve god status with it if you play LeBlanc the right way ;P

Build 2 is more like a theoretical poker build and I admit if you're seriously hit you're done ;) I tried to build it several times but it's unlikely to get the money for all the items.
True, as LeBlanc you rely on champion rather then minion kills and I included Kage's Lucky Pin to improve your income but nevertheless you miss early damage and build slowly to a squishy war machine. A positive effect is that you doesn't really depend on blue buff.
Try it out if you like it ;)

Advises

Don't let yourself fooled by hp, mana, ap and mana regeneration stats in the top info box - Rod of Ages and Athene's Unholy Grail grant further stacking or percentage advantages which are not mentioned. Masteries and elixirs aren't included either ;)
So with about 750 AP you're a real killing devil!!!

Don't ever come along without health pots and wards by each return from base. EVER. It is crucial and definitely worth every 1 gold. Until you get Hextech Revolver for saving you the money.
Still, if you're able to ward important spots on the map you can help yourself and your team alot. Crucial spots are baron, dragon, red buffs, blue buffs, walls and brushes where your enemies like to hide aso.
Always buy pots and wards!!!

What should I say?

General and most common caster runes and masteries, nothing to explain ;)

You can change them, though, but I don't advise it.

Feel free to give your opinion since I am willing to improve ;P

I'll tell you once more: Note that this is my own and free way to think about playing her - no reason to vote down just like that.

If you have serious doubts, let me hear about it ;)
Give good reasons for doing so. Would help me alot!