With my own understanding this is what you can do
Start the description with Greeting
Describe your service with in 1200 characters
Use the editing options Fiverr have provided. (List, Highlight, Bold)
Add the relevant keywords creatively
Include what are the benefits your clients get
Describe why buyers should choose you
Describe the value of your service
Following these proven tips to write your gig description will positively affect your gig ranking. In my research Fiverr loves the creativity and where the buyers are mostly remained. So, make sure to write your gig description that any buyer can read it in curiosity.