A single T8 or T5 NO [not HO] tube will be sufficient. It is up to you if you go with a custom hood made for the tank, or alternatively buy a glass cover and a single-tube fixture. Check out prices locally or online, I know the glass covers are relatively inexpensive but I've no idea how the cost of a full hood with a fixture compares. Once you have the fixture, a full spectrum, natural daylight, enhanced daylight... whatever they call it, tube with a kelvin rating around 6500K will work. You can buy such tubes at hardware stores, made by Phillips, Sylvania, GE. The length of tube will have to fit your fixture.
T8 refers to the diameter of the tube, and T8 and T12 are the type that have been around quite a while; T8 is thinner than T12 and said to be more intense light for the wattage, and longer-lasting. T5 is newer, and comes in HO [high output] and NO [normal output]; the former is more common, but in my view provides too much light intensity. I just posted in another thread on algae troubles when the light is too much for the balance, you might want to have a read to see what I'm talking about. quick question about balance
There is also some more detail in Part 4 of the 4-part sticky series at the head of this section on setting up a low-tech planted aquarium.
T5 tubes will not fit T8 and vice-versa, so you need to buy the fixture for the tube you intend to get. I personally would go with T8 (regular), as the tubes are less expensive than T5 and more readily available and last up to three years. The T5 supposedly use less energy, though I cannot recollect the exact numbers to substantiate if this is the case or not.