If you like political - themed stories, start with 'V for Vendetta'. It's not too complex to begin with and will draw you into the world of DC Vertigo graphic novels. Or, if you're into more modern - day fairy - tale - like stories, 'Fables' would be a good start. You can also check out reviews online to see which one might appeal to you the most.
You can start by picking up 'The Sandman'. It's a great entry point as it has a very accessible yet deep story. You can find it in most comic book stores or online. Another option is 'Watchmen'. It's a classic and reading it will give you a good sense of the high - quality storytelling that DC Vertigo is known for.