Ok the way I got my moon was using fire+storm from 7pm-6:59am I have not yet gotten sun
I am a roockie but I got this guide and it has been useful hope it helps u too
*Sun and Moon Dragon are based on the time you set on your iPhone
*The time exchange for a Moon and Sun dragon is at 7AM/PM. Meaning if you breed from 7AM to 6:59PM you will get sun. If you breed from 7:00PM to 6:59AM you will get moon.
*To ensure successful breeding of Moon Dragon or Sun Dragon in Dragonvale please set your clock to 12hours with AM/PM*not*24 hours.