Unless and until you don't bring traffic to the blog, it won't work. Blog is a good option to promote affiliate links but that should get traffic, either free or paid.
Another good option is to create App, eBook or tools related to that topic and spread that in market via multiple channels. In any case, you have to bring relevant traffic to that affiliate link. In case of SEO result, you may use the following formulae.
Monthly Traffic on the blog post - 10,000
People who click on affiliate link - 3% i.e. 300
Conversion rates -:
SEO traffic - 30%
Social Traffic - 10%
Email - 2%
That means if the traffic comes from search, you may have 90 sales. In case of social media, anything between 20 - 30 sales. In case of email, 6 - 10 sales.
I hope it clarified the expectations.
*numbers are just approximate values. For different blog posts, it may vary.