you can grow them in sand, im using tahition moon sand, but any sand will do as long as its meant for aquariums. Just be sure to rinse the sand well since there will be lots of fine particulate in it that can cloud the water easily. There is an issue where sand can compact the roots, but i've not had this happen. THe only issue i've found was that its more difficult to plant with since its easily disturbed.
btw plants dont need good light, most will do fine with moderate lighting, the more light the more your plants hunger for nutrients and co2
The best advice I can give you is to research which plants to buy to make sure they are low light. There are few better ways to throw your money down the drain than to spend $10 on a cool looking plant, only to helplessly watch it melt away because you don't have the $100 light fixture it requires to thrive.
If you are starting out with low light plants you should not need a nutrient-rich substrate like Eco-Complete. Sand will do just fine, and if you want you can put some root tabs in it. Generally lower light = slower growth = less nutrients & fertilizers required so as long as you stick to the basics you should be fine.
Root tabs are fertillizer that you submerge in the gravel and under the plant. Some plants like amazon sword, they take in their fertillizer with their roots more than the leaves, this is why root tabs are being used. And ofcourse, stronger roots! =)
And if you've been reading, my tank got wiped out my Jello CO2! Since then, I have completely ripped everything out to regrow!
Sand makes it harder for roots to obtain nutrients so it would be better to get stem plants which obtain more of the fertilizers from the water column(through leaves and roots growing from the nodes). Hygrophilia Polysperma is a good choice and hairgrass spreads fast in sand for some reason.