Honestly, the Real Book is such an expansive resource and there are so many ways to interpret the material on its pages (those leadsheets serve more as a rough outline than a factual representation for many of those tunes), I don't know if there is one place to really start. My suggestion is to let your tastes be your guide. Track down the recordings being referenced by the transcriptions (this, you can do alphabetically), and if you like something you hear, try learning it from the Real Book and explore the head's possibilities (i.e. improvise). The other option is to join a jazz band or or something along the lines of the situation described in this recent thread
. Bands that read charts are good, because you're forced to play something passably, regardless of your personal feelings toward the music, and you can also learn from the other players.
Whatever path you take, it would help immensely to learn the history and language of jazz. Are you aware of the effect World War 2 had on the direction of jazz? The answer to that question is fascinating, and outlines some rather significant developments in popular and classical music worldwide ever since then. When you learn the history and culture, start listening to and playing the music, you'll make all sorts of connections and draw your own path through the Real Book.