First, you have to learn the basics of flutter and dart so you can learn them from the Acadmind course available on Udemy.
Now start making some simple apps like News App, Weather App, Quiz App, etc. For this, you can take help from Youtube.
Now start learning about Bloc(state management) and some intermediate and advanced topics. The best source for this is to learn from the Youtube channel name “Resocoder”.
Start learning about the architecture in android development by watching these two playlists from Resocder:- TDD and DDD
Now practice the same apps like news app, weather app, quiz app, etc. using the technique which you have learned in stage 3 and stage 4.
Now you are good to start with your apps and making your projects.