As far as not reading the first book? Yea, not reading the first book.
HBO did a great job adapting the first book into the first series, but it wasn't a perfect adaptation. It's really difficult to transpose everything in Game of Thrones books onto film. In the books you get a glimpse into the inner thoughts, feelings, and minds of the POV characters and get to experience their motivations and emotions. You miss out on that type of thing when just watching the the show (even though the actors do a great job, as well as the directors).
For instance, in the first book, the part where Dani "hatches" her dragons is much more powerful than it was on the show. You feel like you're in her head hearing her thoughts as she's going through the process of entering the pyre to hatch the eggs, where as on the show you're literally just watching it.
It's a much more encompassing experience reading the book over watching the show.