For most homebrewing kegging setups, we recommend 5 to 6 feet of 3/16"" hose. This diameter and length is roughly the amount you will want to use to maintain proper carbonation levels in your beer, and to pour a proper pint without too much or too little foam when you have your CO2 regulator set in the range of 8 to 12 PSI.
There is a lot more analysis one could do to get exactly the proper pour and carbonation from your system at the temperatures you serve at, but suffice to say, this length and diameter tubing will be good enough to serve your homebrew.
Tweak the pressure until it suits your needs. If you are running your dispensing hose for 10 feet or longer, you will likely want to use 1/4"" tubing, as it imposes less restriction (.85 lbs./ft.) on your beer flow and allows you to maintain a carbonation and dispensing flow balance.