I find light to be highly over rated as the major factor. I also find it is almost impossible to get a clear answer to what is needed. That left me to go with a low cost but highly adapable system.
If you can nail together a rectangle of wood to set on the tank top, the ultimate in cheap is hanging CFL twisty bulbs on a cheap extention cord. Clamp, strap or nail temporary construction bulb holders to the wooden frame and keep changing until you see what you want. The bulbs run around $2 and the holders the same. When you have a better idea and want to change out the lighting, use the bulbs in your house. I used four 13 watt, 6500 K for my 20 gallon and was quite pleased. Specialty bulbs are not needed. But they may cost more than the entire DIY lighting system.
When I see T5 bulbs priced at more than $10, I don't worry the question of lost lighting due to poor reflectors. I just throw on another $2 bulb and keep going.