I've remained out of this thread until now because I answered your identical questions last time in the previous thread. But as you seem to be in a corner, I'll try to help, that's what I'm here for.
Get a decent tube for your light fixture and you will be able to grow a majority of plants. Stay away from high-light requirement plants like substrate hairgrass and babytears, etc. I can guarantee you will have no trouble growing crypts, most swords, Pennywort, Anubias, Java Fern, Java Moss, obviously any floating plant...quite a variety for a nice mix in any aquarium.
Decent tube means a full spectrum 6700K. Try a less expensive brand from a hardware store, say Phillips, Sylvania or GE--they all make tubes with around 6500K and call them daylight or enhanced daylight or daylight deluxe or similar. These will only be a couple dollars in hardware stores. If by some chance this does not provide enough (with the window light you mention I still think it will), then a more expensive tube like the life Grow which has a special coating on one half of the inner tube to direct light better would probably handle it. Just understand that you will be a bit limited in plant selection; most stem plants require more light than substrate-rooted plants and those mentioned, so avoid them.
A comment on the substrate issue: it is possible to grow plants well in almost any substrate. But each has pro's and con's that you should consider carefully.
Sand takes considerably more initial cleaning (some of us find this an issue, some don't). It compacts much more easily than any other substrate, and the deeper you have it the more chance it will compact; one member mentioned keeping it less than 2 inches, which helps the compaction issue but will not provide adequate depth for Echinodorus (swords) other than the pygmy chain sword. E. bleherae and similar swords require at least 4 iches as they have very extensive root systems. More regular and careful "raking" or poking of the sand is essential to prevent compaction which causes the plant roots to rot not to mention other issues in water quality for the fish. Malaysian trumpet/livebearing snails help in this by burrowing through the substrate. If you are prepared for the additional care, there's nothing wrong with sand. However, I know of no plant author who recommends sand on its own for a planted tank. That doesn't mean it can't be done, obviously; but just as obviously, there are issues.
Gravel is still a frequently-recommended substrate by plant authors although soil with a gravel layer on top or one of the enriched substrates are becoming more common. Gravel on its own works fine; I have used in for more than 20 years now with excellent plant growth. Small grain gravel is best, as it provides excellent plant rooting medium and allows for good circulation of water (essential) and good aerobic bacteria growth (also essential). Plants like swords and possibly crypts that benefit from substrate nutrients will grow fine in regular gravel though using plant fertilizer tabs/sticks does improve their growth; but it is not essential.
Soil, provided it is plain and contains no fertilizers (terrestrial soils with fertilizers cause innumerable problems because the "fertilizers" are not geared to aquatic plants requirements) works well as a bottom layer; a layer of gravel on top keeps the soil where it belongs as on its own it is easily stirred up. Care has to be taken when planting, and any re-planting will obviously create a mess as the soil will get into the water. And according to Diana Walstad who certainly knows this method, it takes a few months initially for the tank to balance, during which there can be issues.
Plant substrates like Eco-complete and Flourite. These work fine, just like gravel except they contain nutrients. They cost a lot more than regular gravel or sand. They provide substrate nutrients for plants which will obviously grow faster than without, but as mentioned above plants will grow healthy and well in plain gravel or sand so it is up to you if you want to spend the additional money.