This answer is simple, as soon as you have a game idea.
You don’t need to start building a ‘player audience’ from the start, this will come later. Once you start with the development of your game you can get social media channels for the project.
At the start, I recommend growing the awareness of your project within the developer space. Developers love to support each other so this is a great way to start building the foundations of your community.
This is a statement I hear all the time and the answer is often pretty simple, you’re not being social enough.
Don’t get me wrong, regularly posting about your game and updating about progress on social media is great, but it’s only half of it – you’re hoping people find your game first.
The clue is in the title social media, you simply need to be more social. Comment on other developer’s posts you like, share other developer’s work that inspires you, interact with comments on your posts. All these steps will help people see you as an active community, not a plugging machine only promoting your game.