You really don’t have to start your own publication if you don’t want to. But why not keep all your previous and future posts in one place? Maybe someone will read 1 article and be drawn to the next. They will see you have a logo and a whole list of articles. Some people fall for form, some for substance. Why not name it after your Facebook group? Why not collaborate?
You don’t necessarily need your own publication. But it’s better if you intend to stay here longer and grow your audience.