Jennie, both Paul and I use sand in our wild tanks the substrate we use can be found here As long as you don't go with the super fine play sand and get the propegating sand, you will be right. You can find it at bunnings (I use the brunnings brand in the yellow bag - you find it near the potting mixes and seed raising mix) Paul found it was cheaper to go to the local landscaping supply store and get the sand from there... You'll have to ask him what to look for and prices.
Plant wise, if you go for low light plants (java fern, crypts, val, mosses etc), you don't have to worry about fancy lighting. You may have to add a DIY CO2 setup like Adam posted above, but it is dead easy to do.
Also do a google search on natural planted tanks - yes, they use soil (you can also use the sand substrate above for a natural planted tank), but you can cap it with just about any gravel you like. The whole idea is that it is low maintenence once the plants have established themselves and it is a cheap option.
You can use gravel alone, of course, but will need to use fertilizers to obtain good growth and healthy plants.
At the higher price end, you can get something like aquasoil that looks more like small rounded black gravel than actual soil. Bear in mind that this does break down over time.