It's a long, long job to research your keywords, keyword phrases, LSi's etc and then to write content for your chosen search term that has the perfect keywords, and the perfect density of those keywords. This plugin looks at the top 10 Google SERPS for your search term, compares them to each other, and then tells you the keywords that ALL the top 10 pages are using in their content, PLUS the density of those keywords. In less than a minute you will know EXACTLY which keywords and their relevant density to include in your website copy so that it matches Google's exact keyword expectations. Click here for more details.
I've ranked websites in the past with spun content, and now they are still on #1 position of google. First year (2014) google found me because my spun was really bad, many paragraphs were just copied and my position drop from #2 to around #20 after a panda update. Later I cleaned all my text with better spun (I didn't buy any article!), my ranking went up again, and with more backlinks I reached #1 and it is still there