Substrate (bottom of your tank) essentials for your aquarium, it's your canvas.

Substrate advice abounds and I have read some really baddd advice that nearly got me into a serious mess in my tank (basically taking potting soil mixing with loam, and then covering it in sand). I found a substrate that is working great, but it still turned out to be CONSIDERABLY more work that I imagined. And the price was expensive.  This will be a good post to read so you can avoid some mistakes and make the best choice for yourself.

The first bit of advice, if you bought some sort of multi-color gravel or small rock gravel like this

Please return it!  My understanding is with this substrate it is more difficult to clean and it is not ideal for the breakdown for food and waste for the good bacteria. There are many other attractive canvases available including the most simple, silica sand, you can get the white sand from Home Depot for super cheap. I believe it is called playground sand. You will still need to rinse it considerably to remove and "extras".  This sand is good for cichlids or for a tank where you want simple maintenance and high visibility for fish.  You can also get black sand from the pet stores (costs more) for a more dramatic look.  Here is a link with more info on play sand from Home Depot.  

If you considering a planted tank then it get considerably more confusing and the advice abounds. I took the simplest recommendation I could find that would give me clear water (HA! only have 2 hrs of rinsing), good material for the plants to root in and something that held nutrients for the plants so I would not have to fertilize in the very near future. I chose fluorite, at $17 to $24 a bag (shop online) it takes about 4 bags at 15.3 lbs a bag to provide 2-3 inches of gravel for a 53 gallon tank. The advice I have heard from the planted competition sites is that you should slope the gravel with it being 3 inches in the back and two inches in the front to give contour.   Most of you heavy planting is in the back so that 3 inches gives your plants plenty of depth for their roots

Now before you think I am raving about flourite, let me tell you it was a pain in the ass to rinse.  Yes I am very happy with the final product and the plants are growing great, but the rinsing was insane, I mean 2 hrs of rinsing it in the bathtub, if you count the labor involved it is a bad investment. It also left a big mess and the little lady was not thrilled. Here is some ranting on the rinsing and recommended techniques so you cannot say I did not warn you.

I think you may be better in the end going with Eco Complete, it sounds like you rinse it once and dump it based on the reviews here.

Anyway after a week and a few more water changes the water is clear though I still think their is a red tint to everything. I chose three bags of red with one black to give a bit of color variation and I am pleased.

Please note, if you plan on going with a heavily planted tank you will eventually have to use some sort of fertilizer at some point, though I have not gotten to that point yet.