As a general rule of thumb, you want at least 25% more bellows extension than the focal length of your longest conventional lens; however, you should be able to focus a lens of focal length equal to the maximum bellows extension at infinity. Telephoto designs will let you go longer, because the optical node of the lens is actually out in front of the glass. True telephoto lenses usually involve a compromise in optical quality over conventional lenses, but by requiring less bellows length, they may avoid problems of camera stability and wind vibration that come from extending the bellows to the maximum length.

If you're just starting out, I would get something closer to the normal lens for the format, so you can experiment with camera movements and use the camera for what it does best. If the bellows is at full extension, you will usually have no movements available. There are lots of good classic lenses out there in shutters, especially around the focal length for a "normal" lens for each format. What format are you shooting? If you're starting with 4x5", there are many fine lenses, usually Tessar types, in the 135-150mm range, like the Ektars, that are usually quite reasonable priced.