I have sold books and made the best seller list in sales and selling when the book came out a few years ago in 2012. I was working on my next book when I posted. I used Fiver for the cover and was extremely happy with my artist. He also did the cover for the book I’m working on now. As regards marketing, I would recommend using social media - depending on the type of books you’re doing but it’s a great way to attract readers and let your network know you’re writing a book. I’ve bought several from authors on Freerepublic btw.
And of course, there’s no obligation to buy my book for answering questions. Freepers aren’t like libs that always want something. But if you are interested, it’s called The Five Keys To Hypnotic Selling.