Low competition

Hey,

I have a website, in low competinion nishe. My website have zero links count for now. Already in top 3 by main keywords. Got over 20 articles that i want to rank by a different keywords. All my articles already ranking in first or second google results pages. What is the safest way to rank my website and articles for a long term results? After all penguin updates lots of my sites have went down, now i scare to buy any links. How to build quality link profile these days?

Quality links = Quality contents.
You should read here: https://support.google.com/webmasters/topic/6001981?hl=en&ref_topic=3309300