I have been following the "income school" method of niche site article writing and posted 30+ 1000-3000+ word articles all helping the "user experience" and following the SEO basics taught by Income School After 8 months only one post is number one in Google and that was the worst post I wrote, a sort of "100 best snooker jokes" type post. (Gets 2000 per month but not very buyer intent is it). The better posts are still nowhere. Might be a competitive niche, but KW finder didn't think so. I have heard that the usual 3-6 month rule is for very niche sites like homedecoratingskills or similar and that if you try this with a niche like mine, albeit "easy" with KW Finder, you will have to wait 9-12 months. My own story would seem to be suggesting this to be true, although it could be my site is rubbish. I will let you know of any improvement over the next few very important months.
It all depends on your niche, how often you write and publish content, and if you use the Fetch as Google and Bingbot. Try using the Jaaxy keyword research tool. Try to aim for 100+ searches and low competition of 100- or less.