This is a really nice activity to do in your neighbourhood. One person or a group of people can decide they want to hold a regular event for the community, either in a shared space, in an urban garden or in their own garden. Everybody brings along some food and drink to share, in this way all the people make a contribution.
It becomes an opportunity to get together, exchange gardening experiences and get to know each other better. It can also be an opportunity for new people to become involved with the communal space. It can be as simple or as extravagant as you like. Why not have some cooking demonstration or show a film about gardening.