I have an article about a few strategies you can us here: https://medium.com/reciprocall/snag-a-tag-and-receive-top-writer-status-on-medium-bb36f314a9a3

I will warn you, it is long. You can read it when you have time or add it to your list. But you have to write under that tag or topic or related tags or topics until you make leeway. Medium will send you an email when you get a badge in a big topic such as Life, Business, Marketing, Personal Development, or Inspiration just to name a few. There is a list of over 70 big topics and some say it will expand to 100.