/r/startups has a great weekly feedback and support thread. My reccomendation would be to start somewhere small like a forum or an industry Slack channel to get your first points of feedback. Improve / polish based on things you hear. Take a week or two to improve, don't dilly dally. Then take things up a notch by sharing somewhere like BetaList. You can (and should!) think about doing a launch here on PH too.
P.S. not the advertising reddit linked here (clicked the wrong product!) go for the real real :)