We recently came across this 4-part video tutorial on how to edit your subreddit design using CSS (created by YouTuber ThePotatoPilot).
Editing the design of your subreddit is essential to creating an attractive subreddit that matches your branding. It makes your subreddit look official, which sets the tone for how users will participate in your community.
If you are looking for a quick way to clean up your subreddit design, see the /r/Naut community on reddit. Naut is a simple css theme that you can easily install in any subreddit. In the /r/Naut community, you will find instructions on how to customize the theme to match your color scheme and branding.
If you are interested in learning more about Reddit marketing, start here.