If you're going for a low light, low maintenance set up then basic sand will suffice. You'll be able to grow a number of plants including java fern, anubias, different types of hygrophilia, amazon sword and vallis.
If you'd prefer to opt for something high tech with Co2 injection etc then you'd be better picking a substrate designed for plants. There are numerous ones available and they all do basically the same thing although if you're willing to chuck more money at it then you may have better results. Some require gravel on top and others you just use on their own. You'll have to do a little research on what will be most suited to your tank and fish though.
Hope that helps,
Take care,
Jo