The shiny rate in PokeMMO is 1/30,000. You can improve this chance by applying Donator Status or using a Shiny Charm (approximately 1/27,000) or using both at the same time (approximately 1/24,000). Punishments do not decrease your shiny rate.
If you have been looking for a shiny, don't give up. It will come soon or later. Good luck!