Sales don't always have anything to do with good or brilliant or original. Sales are about appeal.
Buy other authors' books when you go to their events. Even if you aren't going to read it. Even if you are going to give it away. Even if you aren't interested. Not just for the author but for the bookstore. It's karma and just plain good manners.
I'm not a good writer. It takes me a long time to get there. I write and then rewrite and revise and do it over and over until I'm satisfied.