I have seen conversion engines run with the magnet taped to the prop. Not nice to look at, but they did run.
So here is what is needed:
Ignition with battery and power switch.
Hall sensor (part of ignition), mounted to crankcase in proper position over/near the magnet to spark at 28° before top dead center.
magnet on prop drive.
The more tools you have, the neater your job can be. Having said that, a good craftsman does not complain about his tools.