crowntail betta

So I've got a Dragon Goby, 2 Angelfish, 1 Pleco, 1 Pictus Catfish, and a Crowntail Beta. Betta? Hmm... but anyways they are all doing great together. What size tank should I be looking at for an end product here? Substrate? I want a really natural lookIng tank. Thanks guiseeeeeee