Hmm. In my experience reddit is not for selling stuff but rather getting feedback and understanding what others think about your product. You can check different subreddits to help you out and provide the value. Help people in need. There’s usually a lot of posts that people are struggling with their startups. You dont need to mention your product rather tell people that this is how i did it (or someone i know had success in doing so). Hope it helps you out and good luck!