Corki is an AD carry, he has some good mechanics and can be really powerful but kinda hard to play. You will need to have a really good farm, and some skill with skillshots , he is based on his rockets (Ultimate).
Garen is a good top laner, he has lots of sustain with his passive. He becomes really tanky in late game but except for that he is a bit useless at late game.. Still a good champion although, and can counter lots of champions in top.
He had his skills changed recently, some to better other to worst, like his ultimate it was kinda a nerf... But let's talk about him in lane, he normally is played at solo top, or jungle . Jax is a dangerous champion, if he starts to snowball he will be unbeatable, but countered by some champions at top,but in jungle he has some good ganking abilities with his stun and leap.
Her ulti... so much damage! So difficult to land and such a stupid mechanic... You can't move while you are channeling it. Still she is a good AD carry. Just needs some good support and she will counter some champions.
A good jungler, he is quick to destroy the jungle, and he has lots of ganking power, with his Q and the taunt. One thing that can be done with him is making him AD , we will push towers like a beast! But usually he is made as a tank.
One of my first champions, he is really good . Really hard to farm with him but as soon as you get Tear of the Godess you will be able to farm with you ultimate and skills. Try it out. Can be played in mid, top or as a support.
Normally played at top, he is known as the troll champion , if you are tanky enough you will just troll people around with your poison and slow.
Normally played at solo top or jungle, he has lots of sustain. A good champion , you should try it out.
Played as AP mid, normally not many people choose him. But he can be a good champion, you need quick reaction to play with it.
A good support, he has heal, his shield and a great stun . So he is a good support. And cheap so it is a good idea to buy him.