2 best websites I have found for almost anything you need for aquariums are...
bigalspets.com (plantedtank.com sponsor)
They will have almost anything you need at the lowest prices around, they are usually half price or even cheaper of local pets/fish stores.
I use regular aquarium gravel for my substrate, so I'm no expert on the fancy stuff. A great place to start looking for info would be the stickied post at the top of the substrate forum called "Substrate articles and FAQ". It will probably answer most of your questions.
Other things to consider would be what kind of water do you have or plan on using, is it low ph, high ph, etc.? Also what kind of plants are you wanting to start with it? There is a also a sticky post on the Low Tech forum for Low light plants as this will be a good place to start for plants. You don't want to start out with some real complicated/tough to grow plants that need special ferts or co2 requirements. A low-tech tank would be best to start with. All of these things will factor in to your substrate choice.
Whatever you decide good luck, and read around on these forums, The Planted Tank forums are a great encyclopedia of knowledge, and a great community of people for continued support and questions.