Transmetropolitan - All the way. I think if your just starting at 14 it might be a bit late for DC (with exceptions) i'd go for Vertigo (Grown up brother of DC). You can't really go wrong so many awesome series.
PS: If you really are a very bright 14 year old then Watchmen is worth a read. It is a little hard going for first timers but will challenge your perceptions of the graphic novel. Is a little dated now though. I'd still say transmetropolitan.
For a complete novice I'd say try them on something they'll recognise, so yes Batman (Year One, Killing Joke, A Lonely Place of Dying), but I first read Claremont's Wolverine in my midteens, and loved it. I recently re-read it and it still rocks. Check it out. Wolverine By Claremont & Miller TPB (Graphic Novel Pb)