Depends on your experience level, in my opinion. Also on what kind of venue you are playing. For a wedding I charge upwards of $200 for my services, depending on whether I’m using songs already in my repertoire or have to learn something special for the dedication. I consider myself a intermediate player according to the level I can play efficiently in sheet music (as labeled). For non-profit organizations that are free to the public, I usually donate my services, but I limit the amount of these types of engagements, and make sure the organization knows how much of a value they are getting in my donation. For non-profits that have events that charge admission, I ask for a percentage (usually 20%) of the house take. It really depends on what you are comfortable asking. One thing I can tell you is that donating my services helped open up avenues-paying it forward works in my experience. But, alternatively, those strings on your harp don’t pay for themselves, so you need to balance freebies with paid gigs. I usually commit to only a couple freebies a year, just for PR reasons.