Corki has been a very strong AD Carry for a while now. His phosphorus bomb and gattling gun work great for clearing waves and he is really easy to last hits with. Corki is very strong early and mid game. If you can get ahead in the early game with a few kills, you will definitely be able to snowball yourself into the late game. It is important to build critical strike chance so that you can blast down enemy carries during the late game.
If you are new to Corki you must remember that your phosphorus bomb does not only damage but can also provide vision if shot into brush or over a wall. Corki is a decently mobile champion because of his valkyrie, but remember that it has a longer cooldown so it can be used to get in a fight, or out of one, but not likely both. Corki is very strong mid game so I would recommend playing quite aggressive as you can afford too since of Corki’s high damage output at a low level. Along with his support, Corki should be able to dominate the early game if played smart.