There are many starter kits for react-native out there. I highly recommend you go through them and pick the one that fits you best, however if you don't know where to start, the recommended place to start is with create-react-native-app.
Create a React Native app on any OS with no build config.
If you do not mind learning and getting a lot of boilerplate, here are some interesting alternatives:
This boilerplate can be the ideal choice for people who already know that Expo is not a great fit for them (e.g: they need modules that are not compatible with Expo) and/or for people that want to use technologies such as redux, redux-sagas and react-navigation since it comes with all of that pre-configured with best practices.