When you play acoustic guitar in any place other than quiet room, you need amplification. Actually the best in your case would be to get guitar with embedded electric pickup. Your microphone can be adequate for studio, but for live show get one of dynamic type designed to live performances. Just try not to bite it. I would still get mixer - you will need to combine pickup output and two microphones (one for voIce and one for guitar). Also microphone preamp with internal feedback destroyer would be helpful.