This is just one approach. Some other states have nurseries where you can get native plants free or cheap.
For maximum effect, you want to connect habitats. Identify your community's habitat areas such as parks, remnant forests, creeks -- anywhere with a lot of wildlife. Make a pinmap. Then target the spaces between those areas and try to recruit people to enhance their yard for wildlife habitat, enabling species to travel from one habitat area to another. Fencerows and riparian zones are most effective for this, if you can convince people to devote that much territory to it. But you can start with yards.