New to LoL!

Hello! I'm fairly new to this game, and it's something I would like to get into. I'm just wondering about champions.

I normally play as Ashe, since I like having ranged attacks like that, but then tried out Ryze, seeing as other players would use him often, and I seemed to like him better.

I'm just wondering, what would be a good champion to start off with? Should I try a new one every game? I like having ranged attacks, but with about average health. Damage output is preferred over speed as well, if that helps.

Also, are there any basic strategies I should know about, or does that all depend on the champion used? Thanks!