This is my first guide, it will be very short.

I play Jinx, as a LifeStealer. At the start of th game, you just need to kill the enemies to rapidly get the Bloodthirster. Upgrade early your Zap and Pow-Pow and use mainly Pow-Pow. Use your Super Mege Death Rocket to kill enemies who have less than 10% of their life.
You need to clean enemies Turrels before you reached level 16.
At the level 16 to 18, with all your items, stay in group to teamfight, you'll be more efficient.
You can lead your team to push mid-lane. Stay follow your allies and use Pow-Pow for damage, Zap for slow enemies, and Fishbones to attack them from a distance !

I need advice from you, tell me if you have some questions !