You don't have to do anything. You can subscribe to as many or as few of them as you want. Yeah - it's a bit cumbersome, but the functionality already exists to search for a community name (like "pcgaming") and get links to all of the communities with that name from all of the federated instances, and then you can just run down the list and click on the link on each one to subscribe to it, and you're done.
When you open your subscription feed, you'll get the posts from all of them, and in fact you'll have to look at the url on a specific one to even know which specific instance it's on, since they'll all look and act the same on your feed.
And no - there aren't any "official" communities, and that's by design, and actually a lot of the point. When there are single, monolithic communities and they go bad, the users often have no recourse. That's when, on Reddit someone would go off and start a new sub and try to draw posters over there.
But here, the damage that assholes and idiots can do is limited by the fact that the content is already spread over multiple communities, and you can avoid the bad ones just by unsubscribing or blocking them, and all the rest of the content will still be there on your feed.