I've figured out by myself that creating stuffs from scratch should be good and easy to understand rather than using those libs. Highly recommend you guys who are react-native newbies like me to using pure react native to learn and build your first app. Cheers

Nativebase is like Bootstrap for React Native app. It is giving you the basic set of components out of the box. You don't have write basic things from scratch. If you are going to customize a lot, then you can do it from pure React Native itself.

For React Native newbies, It will be very helpful to make your work easier.

NativeBase is an open source mobile application development framework that gives you the potential of building applications that run on iOS and Android using a single codebase. NativeBase builds a layer on top of React Native that provides you with basic set of components for mobile application development. The applications stack of components is built using native UI components and because of that, there are no compromises with the User Experience of the applications. Please take a look at nativebase.io/docs/v0.5.7/guide/why-nativebase for more details.