For quick start of creating Android Application
Use fragments to creating screens. Use FlowFragments as containers to separating application into logical parts.
Follow the dependency rules for saving clean of your code.
Use Dagger 2 for implementation this pattern. You can separate Dagger Components into Subcomponents (for each feature or logical part).
Use Room for local storage.
Use Retrofit 2 for communication with server.
If you want use hard backstack, you can use MultiStack Navigation.
Use GoldExtensions for simple using it.
Enjoy!