When you are striving to be the best one man band, you need to build on each performance. (This is also referring to the best one woman band)
First you have to research just what a one man band is or what are people looking for when they hire a one man band.
Are they looking for ambiant music? Music to party? or some variation there of?
You will need the right gear to go it alone.
PA (sound system)- If you are just doing ambiant style, a smaller pa will probably do. If you are doing the party/dance style gig a bigger efficiently powerful enough amp will be required.
Music Amplifier – If you are using a guitar, keyboard and/or drum machine you may not want to put everything through your PA. I prefer this as I can adjust the volume and crunch of my Chapman Stick without effecting the vocal sound.
Microphone – A good unidirectional or cardiode mic is best… you get less feed back.
Your instrumnet(s) – I use a Chapman Stick, some percussion and a drum machine. I like to have easy to get to volume control for each instrument.
Optional Looper – I use a looper, not to layer several instruments, but to create a drum/percussion groove to play over.
Now once you have all the gear it is time to get to work…
Repertoire, song lists, learning the songs, rehearse with the gear and making useful arrangements.