How to market for feedback?

As of now I have a functioning tool I made for myself but then turned into something much different. Essentially it just helps maximize credit card rewards for people who usually just blindly swipe. I have no experience but again, thought it could be useful. I’m in a stage where I’m not so much looking to market it for business but to market it for feedback to allow fixes. Reddit has a lot of communities that this tool pertains to but can’t get the word out without it looking like spam self promotion so where do I turn? Thanks in advance!