-to harass your opponent whenever you get the chance because you can just w out
-when your opponent is driven out of the lane get a level advantage or take out the tower
-your harass combo is w,q,r,e,q and that will knock them down to low to no hp
-to get away use e,w,r
-leblanc is completely combo reliant so if you don't have enough mana to harass don't try to harass(this doesn't apply to using your spells to get away)
-always take mid
-if you aren't doing so well sell you soulstealer because it isn't worth it, and get a blasting wand or level 2 shoes
-try not to get focused, I know this isnt really in your control but if you are getting focused w,r out
-remember to get blue whenever you can
-remember to avoid cc and their team has heavy cc get merc treds. if you do get cc'd you dont want it to be for very long.
-leblanc can deal with slows (not particularly well) but stuns will kill her in an instant
-if your early game isnt going too good then instead of a mojai's feel free to get more doran's rings
-if you feel that your dying too easily then you can buy a rylai's instead of an evil tome

pros
-amazing burst
-great against squishy targets
-good sustain with mana regen runes and masteries
-very easy escapes with w
-can dominate the lane early game
-baron steal easily
-can flash into battle to pick of squishies

cons
-you can harass tanks but not take them out that easily
-starts to drop off late game if you don't get fed
-she can't take a hit
-the laning phase can be very difficult if you don't get an early level advantage

-remember,if you have blue, its fine to use your spells to farm because it may be hard to last hit as leblanc.
-go mid because csing is hard enough as it is as leblanc but also because you need level 6 before you opponent thus, the mastery choices.

-you can usually w in and take out their squishies but if they have a heavy cc team then try to avoid that. remember that you aren't a sustained fighter so the only role you can really play in teamfights is taking out someone that is low or their backline squishies.
-you should be buying wards very frequently, if you have a support then it is ok if you don't but it is still prefered even with a support on your team, remember to play safe because you are squishy. im not telling you to turret hug for the entire game, but if there are mias on the map dont over extend and try to take the tower but as you can get away with w, cc is very deadly to leblanc or any squishy for that matter.

leblanc can deal brust damage that is unmatched so remember to use this to your advantage by w, combo and w again to get back. but only do this if you can see or know their item build and you are sure either you or your team will get the kill

-max your q then e then your w because it is mostly a utility spell and take your ulti whenever you can.
-if you can then try to use your r with your q in mid to late game for any harass because that will do the most damage

if you are taking mid then you can also take teleport but I like flash because paired with your w, you are almost impossible to kill because of your mobility unless of course they have any cc.

my choices of masteries was because leblanc is best when she can chain her spells, the cooldown reduction and the mana regen will help with this. it is always helpful to have ignite and flash up because they are the most useful of any summoner's spells for anyone with the exception of support.

this rune setup will allow leblanc to have complete dominance early to mid game while still having enough ap@18 to still be decent late game. there is nothing worse to leblanc then having to back early game because you are out of mana, trust me i have and it lead to the destruction of my tower. which is why teleport is also a viable option for summoner spells.

-stay in the back to do as much poke as possible and only pop in if you are sure that they won't cc you or you will be getting a kill out of it.
-if you do get cc'd then use zhonya's to prevent further damage
-try to build yourself so that you will dominate early game.
-one of the most common mistakes you can make as leblanc is that people think that they will just win the game upright as leblanc in the early game but this is not the case because she can aslo do tons of damage in the late game aswell