The only advantage of having 3 phase connection is balanced distribution & consumption of energy across the load.
NOTHING extraordinary.
There is a device called POWER FACTOR [ it is a high capacity capacitor bank ] which can be installed over all 3 phases for " actual " energy conservation., a savings upto 15% of energy bill has been reported by POWER FACTOR users. It is a substantial investment over all 3 phases but worth every penny of it. [ there has been a healthy discussion of the unit some 3 years back over this forum please use search option you may find it if not archieved ]
to keep unit consumption low, use LED lights for outdoor usage during the dark hours, install automatic switches which completely shut down supply to a room when there is NO Human inside.
make a habit to switch off appliances instead of leaving them on STAND-BY.
somebody i know have replaced all perimeter lights & indoor room lamps with Philips LED lights [ brand name is expensive but comes with a warranty of free replacement ] The evening unit consumption has dropped significantly from 9 units to 6 units between 6.30 pm to 5.45 am every day.