I created my own subreddit and if you look at the sidebar, it is clearly promotional content. I post my own stuff and have links to my website in my sidebar. It works pretty well and I don't get complaints. Its a fashion sub so I cross-post pictures, but otherwise just post my own stuff and answer people's questions. It helps that I promote other businesses as well, not just my own links.

Overall, I found it a good marketing tool for my side project and a way to not get into trouble with other mods. You can see it here: https://www.reddit.com/r/Watchbands/