I think around 20. But you'll get more sales with more posts. Being consistent is the key. Always do your research and write more content. Hope this helps.
Raynold

I agree with VitaliyG. I take his advice. Keep producing cool content.
All the best
Jane

I always tell people to give it 6 months and aim for 50 blog posts. Your site gets more recognition and higher rankings by that time and all the work you put in with earlier blogs starts to rise higher in search engines, snowballing into large numbers of traffic.