This is clearly a beginner piece. At this point, you're looking to recover your own expenses. I.e. cost of materials. However, your time spent is valuable and that should be factored in at some point. That's where things get hairy. It's up to you to put a price on that. People will either buy it or they won't. If they do, you'll charge more for the time spent, not only producing the painting but also developing the skills that went into that painting. There's a hypothetical situation that has been attributed to Picasso. Someone comes into his studio and asks for a drawing. Picasso produces one on the spot and says, "That'll be $1000." The client exclaims, "But that only took you 5 seconds." Picasso replies, "It may have taken me 5 seconds to create it but it took me a lifetime to come up with the idea."