Most likely, no one will read your messages if you're casting them to a channel that hasn't approved you, or writing to someone who isn't following you.

So, you should focus on two things:

1. Only send messages and react to people who are following you.
2. Create interesting content that makes your followers quote your casts, helping you gain new organic followers.

I've gathered 300 of my active and interesting followers that I'll be interacting with. I've organized them by priority, divided into 10 groups, and sent them to myself in direct messages.

The rules of the game have changed, so make sure to adapt.