A gas will most likely behave ideally when the following is (are) met:
the gas particles do not attract or repel each other.
the gas molecules have no sifnificant volume.
the gas molecules are crowded together.
the gas molecules have significant attractions to eachother.
The gas will most likely meet the condition(s) of the ideal behavor at:
low pressure, high temperature
high pressure, high temperature
low pressure, low temperature
high pressure, low temperature
standard temperature and pressure