You will need a website for your graphics design business and will also need a portfolio where you can list and show some of your best graphic design work/projects.
You will need to set up a website correctly for your graphic design business in order for you to profit through a website, you can do this by setting up a business website for your business with the tips at Your Business Website.
You can set up a portfolio of your work by creating an online portfolio on your website and/or on some third party sites like behance.net etc. You can also create a physical design portfolio for your design works too.
Your portfolio can comprise of the best
- Jobs/projects you have completed or done for some clients
- Job/projects you did for free for others
- Self-initiated or personal design projects
It can include designs for different applications and the specific niches you may want to sell to.
You should generally provide some context for each of the design work/project, that you may have in your portfolio, in order to show how you interpreted the accompanying creative briefs for your design works. You can do this by including some notes and annotations on how and why each of your designs were created.
You will need to regularly update your portfolio with your design work. You can include some case studies with the projects that you have in your portfolio, and some recommendations from your clients too.