If you have the "standard" dual light fluorescent tube fixture, it is likely T8. Check the tubes you now have, at one end it should say T8 or T5. Or tell by the diameter, as the "T" is the tube diameter in 8ths of an inch, so a T8 is 8/8 or 1 inch diameter, a T5 is 5/8 diameter. The tubes are not interchangeable.
Assuming it is T8, then two "daylight" tubes will give you moderate light which will be sufficient for the majority of plants. This is all I use, you can see photos under the "Aquariums" tab below my name on the left.
For two 48-inch tubes (assume this is what you have over the 75g tank) you can go with those from Home Depot or similar stores. GE, Phillips and Sylvania all make some type of "daylight" tube, look for the Kelvin rating which will be 6500K. I use the GE and Phillips, and have used Sylvania.
On the substrate, I agree with play sand, I use Quikrete from Home Depot. Fine gravel can work too, but sand is better for certain fish like corys, loaches, etc. Dirt with a cap of sand can work, but I do not recommend this when it is your first planted tank. There are some issues with using soil, but these do not exist with sand or fine gravel. I have never seen the benefit of soil, so my 7 tanks all have play sand (in 6) and fine gravel (in 1).