How many local cities should I target first for new plumbing client?

Noob here, For a new plumbing company I'm working on, should I target the city it's in that's not very big first until it ranks high? Or should I target the surrounding cities as well? If so, about how many?

They already rank 1st in the map pack for the keyword plumbers in the city it's in but not in organic search. How do you guys approach local SEO for companies that want to rank 1st for relevant keywords in their area + surrounding areas?