$2.53 isn’t much of a test, probably need to run at least twice the value of a conversion to get a general idea of how it converts.
CTRs and conversion rates vary a lot by channel and by targeting methods. What network are you testing it on? What targeting methods are you using? How granular is your segmentation?
The first thing you need to do is establish a benchmark for your campaign, then analyze the segments within your campaign to determine what your audience is responding to the most. Does the offer you link to provide any kind of analytics data? If so, use that data to evaluate the segments of your traffic.
Another thing to consider with Affiliate offers is whether the conversions are being tracked accurately, which has been a major problem with many affiliate programs.