First, it takes time to make good amount of money on Medium. People who get good traffic in short time are the one who have a large fan base on other platform or really good marketers.
The second thing is to be active on this platform. A copywriter once contacted me a year ago, and want to help her part of the Medium partner program, I helped her and she just published two posts till now. So, the problem is consistency. Be consistent and learn things.