Based on your experience, how long does SEO take?
 

Based on your experience, how long did it take you to get decent traffic from search engines?

For me, I have been doing SEO for more than 1 year, and I still get 70 visits a month. I know it's bad.

What is more important, higher ranking or high indexed pages?

70 visits/month. I think that this result is bad.
I think you should learn more and apply SEO for your website. You can consult about SEO at link searchengineland[.]com/guide/what-is-seo

It depends upon niche. But average it takes around 3-4 months.