Read em
I have read them all several times. It would be difficult to state a favorite. In the set of books I received as a kid a long time ago, LWW was number one in the series, so it was the one I read first, and I LOVED it, so it is probably still my very favorite, but they are all good. That set of books has stayed at my mum's house, but if I am not mistaken, the Magician's Nephew was about number six in the series, despite it tells the story of how Narnia was founded. Each of the other books has something to recommend it -- read them all is my advice.