The answer depends on what circuit the transistor is put into. For example, do you intend the transistor to operate as a switch, or as a linear amplifier or something else? The VCEsat in your circuit (assuming a common emitter switch configuration for now) is a function of the load resistor, the power supply voltage put to the load resistor, the base current, the HFE and to some degree the temperature. If you want to consume little power, then make your load resistance relatively high so that very little collector current needs to pass through the transistor. In this case you can find the HFE from the data sheet and interpolate or estimate from the values given or the graph given. If you intend your transistor to operate as a saturated switch, you should overdrive the base current to some extent to insure complete saturation for lowest VCEsat. I could suggest some values but this is a waste of time unless you post a schematic diagram.