Daniel,
don't give up quite, yet. You get the views, you'll get the sales! My business is slow, too, and stronger local, but hang in there as people have mentioned and they gave you lots of great advice! I just changed many of my pictures! It is a lot of work. A good advice that I received, take 30 minutes each day and dedicate them to something specific. Don't get of track and don't do any more, e.g. Wednesdays pictures, Thursdays Tags, ... update, improve, change and use the statistics to adapt your tags and titles.... That might help, too. Good luck!