When you invest money in a road bike, its well worth it. There's lots of enjoyment in riding. Even though your goal is triathlon competition, it is quite natural to ride with others. Most other riders have road bikes anyways. I wouldn't consider spending twice, once for road, once for tri, as a waste. You will find out that they are different in its application and in your everyday usage. Think of it as "double the fun".
I started out with a Cateye wire and then Cateye wireless and now a Garmin 305 GPS.