Finding an instance that doesn't block other instances, but also actually moderates its users and thus doesn't get blocked, is going to be pretty hard - and also a rather harassment-filled experience unless you fit in with the Gab crowd, I imagine. You could always run your own instance.

Note that the majority of instances that are "blocked" are actually soft-blocked by most instances, meaning you can still talk to people on them if you follow them, you're just not going to find posts from their users otherwise.