Congrats! The life forms that will eventually grow is really fascinating. In mine I have 3-4" of sand (w/1 cup of live sand from the tank), about 1" miracle mud, mix of algae. I have caulerpa in there so need to keep the light on 24/7. I had a bad experience with it last year and left the light out for a couple of days and it went asexual, my whole tank turned soupy green within a matter of minutes of turning the light back on.
I'm sure other people have there's setup a little different, I"m also anxious to read other comments.....