Each character does something different, I assume? And there's sooo many of them from what I've seen. Which of the champions would be good for someone who likes staying back from the battle, but helps from the long range?
other sites for builds/guides:
mobafire.com and solomid.net
Stay away from sites like Leaguecraft and Mobafire. Its better to learn on your own then to have a list that you need to look at.
For you preference, I would go with Ashe, Tristana (build DPS), or Kog'Maw.
What's ELO exactly? Noob question, I know.