This is purely theoretical. Ignoring the demand for power, how would Iron Man's suit be constructed? What would be the type of flight he uses, or type of repulsors? An idea I had was that he uses a thermal thruster or chemical thruster for the bootjets. The repulsors use VASIMR or some basic ion thruster as "flight stabilizers". When he uses them offensively, he has a Van de Graaf generator or Tesla coil making electricity, which discharges through the path of ionized gas that also comes out of his gauntlets. Or he could use an ultrasonic transducer with focused intensity, particle displacement, and pressure.
Any ideas? I know the suit is just in a movie, but I'm curious.