What should a successful design portfolio contain?

After Ben Cox's talk, I had a better understanding of what a successful portfolio for illustration should contain - 
Maps, Typography, Food, People, Landscapes etc.

As I'm hoping to market myself as more of a designer, this inspired me to look into what elements I should be aiming to include in a design portfolio, which would be something to work towards over summer.

SAMPLE PRETEND (but still real) PROJECTS
1. The DREAM client website
2. The non profit or mom n pop website
3. Your twist on an icon set
4. Improved mobile product UX
5. Redesigned newsletter template
https://skillcrush.com/2014/08/11/portfolio-advice-2/

What to include in your graphic design portfolio:

https://www.nyfa.edu/student-resources/what-to-include-in-your-graphic-design-portfolio/

Some things I can think of off the top of my head:

Logo design

Poster design

Motion Graphics/Gifs

Publications

Illustrations

Web Design

Font Design