If you have not used a spinner before then I would suggest that you first use something that require more human imput like The Best Spinner or Spinner Chief in order to understand the basic principles. However if you must go fully auto then I would suggest you go for Wicked Article Creator. I have it and understand it is similar to wordAI but a one off fee of $47.
A website with lots of unique and human-readable content is going to give you the best ROI. The more quality readable content your website has, the more exposure it will get from major search engines such as Google & Yahoo. But creating unique content takes time as you first need to develop content creation strategies and then you need some hours to write a full SEO optimized content. How great it would be if you can produce quality content within minutes! Yes, it's possible with the help of this free Article Rewriter Tool developed by SeoToolStation.