LeBlanc has one of the strongest early games because she can proc Electrocute very easily with Distortion followed by two autos.
LeBlanc’s main source of damage and wave clear is her Distortion . It does have a long cooldown (18 sec at level 1) and the best time to trade with Leblanc is when it is on down as it severely reduces her mobility and trade potential.
Do not push without vision of the enemy Jungler. LeBlanc is one of the best Mid laners at setting up ganks for her Jungler thanks to her .
LeBlanc is an Assassin. That means if she gets ahead of the early game, she can snowball really hard and stomp the game. Do not over extend or trade aggressively when you know that she can kill you.
LeBlanc can push in the early game and move towards your jungle in attempts to kill your Jungler, or roam to another lane. Make sure you follow her roams and ping your Jungler to counter this.
LeBlanc is a heavy skillshot based champion, if she miss one of her skills (for example her), she's really vulnerable. Look to play aggressive while one of her abilities are on cooldown.
LeBlanc has a strong all in potential as soon she hits level 2. Before that, she can trade you with Distortion and auto attacks to proc Electrocute. Make sure you account for this by trading back with her when she goes in.
As soon she hits level 3 she can go for a longer trade if she lands her Chain . Stand out of range or behind minions so she cannot easily hit you with it.
Once LeBlanc gets Ludens, she can out damage you in every single trade. Do not push too far up without assistance or an escape ability as she can easily look to all in you.