The answer is 0. Spending has nothing to do with promotions on Writing.Com.
The qualifications for promotion include reviewing and interaction on the site, along with minimum amounts of time on the site. The full qualifications are listed in "Writing.Com
101" which is linked from the top of each page.
Promotions are made manually, however... and Writing.Com
is a literal "Mom and Pop shop" -- two people. Active members in our community also know that our 5 year old daughter was diagnosed with Leukemia the first week of September, so they know that this type of manual promotion is not something we have time to take care of right now. We'll be back to it as we work through and manage our family health issues.