Many people say leblanc is OP, In my opinion that isn’t even close to true. You can shut her down easily however that’s for a different guide.
Rune Page
Quints – 2x Flat Health; This is for early game survivability. 1 Magic Penetration.
Marks – 9x Magic Penetration; Probably the most effective from the math I did. With the magic penetration from this and the Magic Penetration Quintessence rune, you get 10 magic pen. With a base 30 MR(23% reduction) this will drop that to 20 MR(17% reduction). Grabbing Sorcerer Shoes brings that down even further to 0 MR (0% reduction); if they don't get MR.
Seals – 9x Flat Mana Regeneration.
Glyphs – 9x Ability Power, or 9x Cooldown Reduction. (I prefer AP, but it's your choice)
Masteries
9-0-21
3 in Archmage’s Savvy
1 in Deadliness (Or exhaust if you choose that summoner spell)
4 in Sorcery
1 in Magic pen
3 in Perseverance
1 in GoodHands
4 in Awareness
1 in Expanded Mind
1 in Greed
3 in Meditation
3 in Quickness
1 in Flash
3 in Intelligence
1 in Presence of the master
Summoner Spells
Flash – requirement on leblanc. Do not trade this for anything else, ever. Do you really need the triple flash? Heck no. But now you can use your W and your R for damage and not risk dying because now your escape methods are on cool down.
Ignite or Exhaust – Counter spell, hard AD carries will need exhaust and Swain, Mundo will need ignite.
Skill Order
First don’t grab a skill. Grab your items and go protect your jungle / gank their jungle. If you’re ganking grab E if not wait. If they come to gank your jungle then grab your E fast and chain somebody important. This forces them to come at your 4v5, run away and leave one chained behind, or wait with their teammate until their unsnared. Your team should be able to get some harass off with this. Hopefully making them back and allow you to help your jungle. After this grab your W then max your Q. (W for escape just in case).
Otherwise lane and your skill order should be
1: Q
2: W
3: Q
4: E
5: Q
6: R
7: Q
8: W
9: Q
10: W
11: R
12: W
13: W
14: E
15: E
16: R
17: E
18: E
Laning Phase
Grab a doran's ring to start out with. the mp5 and HP will help, the AP is like a little boost. Sell it when you're a little short on gold from buying a big item.
Your Q is your main form of harassment. You can also use it to ensure you get the big minion. All the other minions are easy to judge for leblanc’s last hits. Reminder that when you Q you can W to proc off extra damage (including the damage from the W), and get a silence off on your target.
Farming
Its hard for leblanc to farm against strong push champions such as malz, or morgana. Because leblanc has low attack speed its hard to beat the turret to minions. For this I suggest auto attacking and just grab as many last hits as you can. Pop spells if you have to because if you’re not getting kills you need every minion kill you can get to grab your items. I have out farmed solo lanes before on leblanc even though it is difficult it is still doable. Farming on leblanc is a difficult skill I have yet to master.
Getting the kill
Your first attack will probably be your Q+R combo. Because your Q has a proc effect which deals additional damage as well as silencing the opponent. The next thing you are going to do is either your chains or distortion to proc your R. Also resetting the silence timer. The reason why you would distortion is because it repositions you to better hit your chains. However your chains more important to hit after your Q+R.
If you distortion then you're going to want to throw your chains on about 1.5 seconds afterwards. After you throw the chains on try to stay right on top of them if you can. This prevents them from flashing out of your chains. Q as soon as your Q is off cool down because you will likely be able to Q before your chains snare it will proc the bonus damage from your Q.
If you chain first then you are going to want to stay close to them to snare. Next when your Q is off of cool down you should Q for the damage and W to proc off your Q. This will almost ensure you get a kill unless they grabbed HP items and magic resist already. Which they shouldn't have because Leblanc can outplay a lot of characters, denying them farm.
Get some map awareness. Honestly with no map awareness you will die on any champ. As Leblanc, map awareness will give you kills. You see your mid lane going to gank top? push your lane to their turret and when you see the enemy coming toward you go sit in a bush and combo them to death! It doesn't matter who you are Leblanc's combo's are stronger then anybody else's during the laning phase. The reason is because you can pull off 3 silences and a snare if you do it right, and they live that long. You can't flash out of a snare or while silenced, what are they honestly going to do? Auto attack you? CC will carry you to victory. DPS yi with lifesteal should die to your nuke faster then he can auto attack. Q+R Now he can't alpha strike, E Now he's snared, Q+W = he should be dead. Honestly what could he do? can't auto attack to get health back, silenced and can't heal himself, hes pretty much screwed. Leblanc should win 1v1 fights.
One of the more difficult people for me to play against as Leblanc is Vlad. Vlad as the advantage of pooling out of your combo attacks. What you're going to want to do is chain him first. The reason for this is your snare gets him in his pool. Now if he pool's, chase him down. If he doesn't throw your Q before the chains proc off. Then chains will proc the extra damage on your Q, then you can throw in an R+W to finish him off, or make him want to go back to his home stone as your farm more gold.
Team fights
Determine who your team needs to nuke down. And when you see them out of position Wreak their day. It’s a simple Q-R-W combo. Likey somebody such as Xin Zhao will try dash at you and pop you up in the air so that his team can kill you. This is when you should chain and position yourself away from him so that you snare him but don’t get popped up in the air. After the snare your team will probably melt him quickly.
Leblanc’s needs to be in the right position to nuke down other players. Because of her abilities she is really good at baiting the enemy into a bad position. The easiest people to bait out of position would be tanky dps suc has xin xhao, renekton, nasus, etc. What you’re going to want to do in this type of situation is get in an okay position and nuke down a squishy with just a Q->R Combo. Then you have to make a split second decision whether the dps is focusing you down or if they’re going to ignore you. If they ignore you (and you have flash up) throw your W combo onto the person you’re nuking to finish off the combo. Next if the dps gets on you then you need to chain him and run back behind your team. Just make sure you keep the chains in range to pop the snare off.
Your job is to kill the person on their team causing your team the most problems. If they grab a banshee's ask somebody on your team to pop it, or you can just Q them and it will go away. With your Q on such a short cool down it shouldn't be much of a problem. Just Q them before the team fight starts. With your Q on a shorter cool down then the banshee's veil it is very much worth popping. Just make sure the team fight starts 45 seconds after you pop the banshee's.
Leblanc will use the chaos in a team fight to her advantage. Because of her jumping around, the fact she is packing flash, and her passive which creates a fake image of her self helps a lot actually.
Build
You should never build leblanc's items in any particular order. If you're in mid wreaking but Xin is getting fed, you should probably grab a Zhonya's Hourglass, at the same time if your whole team is wreaking I suggest rushing a Rabadon's Deathcap. I will not tell you which items you should always get on leblanc. I will tell you which items are useful.
Zhonya's Hourglass - Useful when dps characters are getting fed. The active can save you in sticky situations also good against karthus.Prepare to pop a flash or a W to escape.
Rabbadon's Deathcap - Ya this item is the king of AP champs. Gives you 201.5 AP by itself also increasing the AP of your other items by 30%. Great item to grab to assist you in nuking people down.
Banshee's Veil - This is a great item to counter other nukes. You're playing against a Veigar, a Brand, an Annie, or even another Leblanc? This item will effect their combo attack, ruining their stun or mitigating the damage from a nuke.
Void Staff - This is a very situational item to get, you would only really get it if the carry you are trying to nuke down has a decent amount of magic resist.
Abyssal Scepter - This item is a good counter a karthus or somebody of that sort because it increases your magic resist, gives you ap, and reduces magic resist of other champs. Grab sorc shoes with this and if people don't buy more magic resist you'll be doing 100% damage from your spells, as opposed to the 77% (74% for some champs).
Archangel's Staff - I personally dislike getting this item on leblanc, because at 16 her ult costs no mana.
Deathfire Grasp - 60AP, 15% CDR, This item is only really viable against health tanks such as Cho'gath maybe viable against an olaf carry or something of that sort.
Mejai's Soulstealer - Snowball item, useful if you find a scrub on their team you can kill every time you see him. Otherwise i dislike snowball items as i find them to ruin your late game when people can kill you anyway. Plus when you stack it up people just want to kill you more, useful if you know you can escape everytime.
Morrello's Evil Tome - 75AP, 20% CDR, the little MP5 doesn't hurt either. I find this item more useful rather than the Deathfire grasp.
Rod of Age's - not a bad item to rush if you're solo laning, grab the catalist and sit and farm for hours. 80AP with the bonus and more HP then the Rylai's. Also gives you a little bit of mana.
Rylai's Crystal Scepter - Little HP for surviving, 80AP is nice plus now all your abilities slow instead of just your chains. Great item vs a Rammus. Also will make your chains a billion times easier to hit due to the slow.