If it is sand (fluorite sand mix w black diamond sand) you need snails to help oxygenate the soil. Sand compacts, where as products like Eco do not. So yes you need something (MTS) in the soil to keep it "stirred up)
Root tabs help when you feel your soil is exaushted. Some of the decaying matter in the tank (plants and poop) get back into the soil but not enough (imo) to keep the soil thriving. Eventually all the ferts in the soil will be used up. This is where root tabs come in. Seachem and API both make them, however also (the link I provided) Bobs sell them at 1/2 the price and for a better product.
Co2
This is based on lighting and the plants you wish to grow. If you want to go lowtech stick with NO (Normal Output) lighting and get plants that require low to med lighting. Plantgeek has a variety of options you can use to build what you wanting to build whether it be by Region, Difficulty, Light requirements.... It will provide pics and a description.
If you go the LowTech option you can use Seachem Excel for your carbon source.
So again What size tank are you going with?