You don’t even need spelling + grammar, honestly If your content is specifically aimed at bots, having a good keyword density is good enough to get your site up in the serps. If you’re also interested in users actually benefiting from the content, then yes, mind your spelling and grammar.
I’d like to add that besides the fact that the content needs to be unique, it needs to:
– have a relevant connection with the title, description and header tags
– over 150-200 words
– be updated frequently (for example, adding 1-2 articles each 4 days is better than adding all 15 articles now)
– be formatted correctly (bolding out keywords when possible, having headers when possible, internal and external linking with keyworded anchor texts, etc)
To write something unique, you must first have your own knowledge on a topic. Then you write what is in your mind… adding your unique writing style to it and angle.
What makes it unique is your personal angle and style.
Try google news. You can always find the most relevant news about a topic, and then get a pretty good education in a short period of time.
If you want to write a article on a topic and you need any idea about it, then search for that topic on the internet, and read about it. Then write your own content and Never copy even a single line from the internet.