Just a Friendly Word of Advice
When playing ranked and you're choosing a champion, you should remember that, that is a critical choice that can very well determine the outcome of the game. You will want to play a champion you can use in almost any given scenario. Think of a situation in which your team is behind in kills and objectives and the enemy has taken at least one of your inhibitors. What champion do you know and understand enough that you can utilize to bail you and your team out of that situation and maybe even possibly achieve victory despite being so far behind? Whatever your answer...that should be your pick.