Add Tristana to the list of recommended ADCs, she has two escapes in her W and R, an amazing AS steroid, and once she levels up a bit the highest auto attack range in the game (which for ADCs makes a huge diffrence).
Also, Minions and towers are significantly stronger in this game, you cannot tower dive willy nilly and expect to get away with it. Try it in a bot game to see what I mean.
Also, the tutorial is garbage.
Oh, and you can get Tristana and Alister for free by likeing Riot on Facebook and subsribing to their youtube channel respectivly --- How does Riot keep it's balance? That I can tell you in one word! http://www.youtube.com/watch?v=gRdfX7ut8gw