Roadmap to learn Flutter
https://www.youtube.com/watch?v=7660DZ_HJqM

Если кратко, то roadmap такой:
-Dart basic
-Flutter
-Widgets
-Git Basics
-Start building
-Design Principles
-JSON
-Networking (APIs)
-Shared Preferences
-databases (SQlite, Hive/Moor)
-Firebase
-Dart Advanced
-State Management (Bloc, Redux ...)
-Animations
-Testing (Unit testing/ Widget testing/ Integration testing)
-Rx Dart
-Packages & Plugins
-Dev Tools
-Internals of Flutter
-Other Languages (little bit Kotlin, Swift, html/css/js)
-CI/CD
-Firebase Analytics
-Manual App Testing
-Deployment (App store, Play store)