Where to begin?

Flutter itself provides ample tools and tutorials to get started at every level, from beginner to intermediate. It will get you started on the right track whether this is your first time programming or you're coming from another language.

To begin, some of the references -

Documentations : 

• Flutter introduction 
• Dart CheatSheet
• Flutter Cookbook for every major topic

Youtube :

• Flutter Channel
• Flutter Playlist - Widget of the Week

Codelabs :

• Google Codelab 1
• Google Codelab 2

Community :

• Flutter on Discord
• Flutter on Slack
• Flutter on Reddit

Flutter Learn has a slew of recommendations with extensive explanations.
If you haven't already, join commudle for more flutter labs coming soon.