One of the proven ways to get SEO without dipping into black hat SEO (which will almost certainly get you nailed by a Google update at some point in the not-too-distant future) is to produce great content.
Even if you have the ability within your team to produce great content, though, great content is a creative activity that takes time and space. Let's say you have a Paul Graham on your team, who can write amazing awesome articles on a fairly regular basis. He still will only be able to write a few of those a month at best (probably less). Push your Paul-Graham-junior to write one article a day, and quality will drop rapidly.
So, how do you scale great content?
The secret is earth-shattering: you hire great writers outside your team. How do you find them? How do you approach them? How do you use them?