I find 5-10 gallons to be the perfect size for me. I have one in a 5.5, 2 in a divided 15 gal so 7.5 gallons each, and one in a 10. It depends on the personality as well...some are lazy and don't need as much space, while others zip around constantly and love a large tank.
Prices vary depending on what type of setup you want. A smaller tank is less money to decorate, but the fixtures cost pretty much the same as a larger tank. There's no shame in decorating as you go along either if you don't want to shell out all the money up front. I've done that before - buy gravel, a few silk plants and a pot and then improving later on to fill it up better and achieve the desired look. You never know when there may be a sale ;)
Last edited by Kim; 08-15-2009 at 08:12 AM.