New champion advice
So I've been playing LOL for a while now. Around a week and a half and I'm level 16. I've got a lot of champions that are cheap unlocked now (Such as warwick, annie, malphite, janna, poppy, ashe, garen, alistar, master yi, etc.) but I'm now planning to get a new champion. One that is really expensive but is worth the cost.
What champion is the most powerful in the game? I don't care about the cost. I want someone who is good at their role, like a jungler, ganker, top laner, adc, or even if it is a support. (TBH I like playing Janna as a support.)
I'm thinking of people like Zac, Caitlyn, Thresh, etc.
Someone worth the expensive cost and who is good at what they do. I'm a player who can play as anyone. I'm flexible. Any category is fine.