Many people have different opinions, and there are many different types of substrate and substrate setups you can go with. But to keep it simple i recommend eco-compete as your substrate i heard people like flourite but i recommend eco-complete. You need to be generous withe the amount, i forgot the recommend amount of inches but i believe it was around 2-4 inches, the roots are very important when it comes to plants, so 2-4 inches should be good. Its going to cost you considering eco-complete isn't to cheap. I'm don't know the best place but i know online will most likely be cheapest, i say try drfosterandsmith they usually have one of the cheapest prices.