I wanted to suggest that you add a function that allows you to search the entire US. Users like myself look for rare or items not found locally.
In order for me to find these items, I have to go from city to city and state to state to do my searches. I believe that if you add the function to allow users to search the entire US, you will have more users visiting your site and using the app. Letgo does allow for this, but their platform is not as good and user friendly as Offerup. Craigslist is also a good site but they don't allow the search of the entire US which I think limits a lot of users.
In order to improve on these limitations of other sites and apps, Offerup needs to do something differently.
Give the user more choices and they will use your app more than these other sites or apps. Thanks Arnold Cruz
Review about: Offerup Website.