It would help to know what you're starting with and what you intend to use it for. I bought a cyclocross bike as a first/only bike last year and its been great so far. I'm not doing group rides or racing, but it seems fast enough on the roads and still capable on the light trails. This lets you sample the riding in your area to see which you prefer. If you intend on having only one bike, then a used CX bike might be a good idea to play around with, then sell it when you know what you want to ride.