I can't really add much other than to echo previous comments - easy to grow plants like crypts and swords (primarily root feeders) will like eco-complete or fluorite (I've used both with success). One caveat about fluorite - rinse it really well first, it is very dusty, and will really cloud your tank when you fill the first time.
The aquatic potting soil comes recommended, but I found it annoyingly "fluffy", which made my tank get cloudy, and it was difficult to plant - it would not hold down the plants. Perhaps it would have worked better for me if I'd capped it with 3M ColorQuartz black sand (which is awesome, BTW - looks great, and the grains are nice and heavy, so when you plant, the grains fall around the base of the plant and hold it down nicely).
For a super-easy low-tech setup, however, stick to epiphytes (plants that grow by attaching to something) and floating plants, and you won't even need a decent substrate. Mosses, Java ferns, anubias, bolbitis will all do well in a low-tech setup. Just tie them to driftwood or rocks with cotton string or fishing line and you're done.
Get some good algae-eaters, though, because those slow-growing plants will have a hard time out-competing the algae for nutrients. Olive nerite snails work well, as do various shrimps, siamese algae eaters, american flag fish, otocinclus, and I think black mollies IIRC.
Good luck, and have fun with it! Needless to say, GWAPA is an amazing resource for planted tanks, and their auctions are chock full of stupidly cheap plants of all kinds.
