As mentioned, your issue is light intensity.
That T8 fixture is probably only 15 watts, probably just enough to grow java fern.
Contrary to common believe that iron makes red plants red, it is light intensity that is needed
Increasing intensity brings other requirements such as Carbon & nutrients.
Biltek LED flood lights are really good and cheap. Could get 2 30watt lights. Will cost about $100 for both. Otherwise Fluval Aqualife and Plant 2.0 those are really good lights with full spectrum also. Current Satellite LED Plus Pro lights come with a ramp timer as well.
I've never tried the Finnex planted lights, but heard they are very good and have seen great growth from those lights.
I don't think colour matters too much. Anything from 5000-10,000K would work well. It's mostly a matter of taste, but if you want to emulate the sun, the sun is 6500K. If you go with fluorescent lights, go with the cheapest shop lights you can find. But if you go with LEDs, I agree with troutsniffer, don't buy the cheapest you find. Do some research first.
Tom, the cost would depend on the quality of the light. As for what you look for, I guess you'd just look at the colour since that's usually the only relevant info provided. PAR would be nice, but few fixtures provide these numbers. Best is to look at reviews and maybe PAR values from other aquarists.