You don't really need to worry about unique - as long as you're not copying an existing article, explaining your own understanding using your own words should give your own perspective.  Because people learn differently, for some people it may be your explanation that "clicks" and helps them to understand the topic.

I would advise taking some time writing articles though. Write up a quick plan of what you want to cover, then write the article, and then go back through and see if there's anything you need to fix or that you can improve; don't just try to do it in one go.

As for "spam free", perhaps I'm misunderstanding, but I just don't see how that could be a problem... don't spam, and your articles will be spam free. Make sure any links are relevant and necessary, and try to write about something useful, not just as an excuse to share a link.

Hope that helps!