It doesn’t matter if your domain is new or old.  If the servers are Windows 2008 or later you could and should use the central store. I have seen both new and upgraded domains that don’t use the concept of the central store.

What is the Central Store

In older versions of windows you copied the administrative templates to each GPO. With Windows 2008 and later you don’t need nor should do so. The Central Store is a directory on the sysvol where all servers can look and multiple policies share the same new admx format files.

I checked I dont have the Central store and it works anyway

Well yes all same level windows have a copy of the same policies in the C:\Windows\PolicyDefinitions directory. But that gives different information based on the client that you used edit the policy. By creating the central GPO store we make sure that all client use the same amdx files.

How do I create a central store then.

Just copy the C:\Windows\PolicyDefinitions directory with subfolders to \domain.fqdn\sysvol\domain.fqdn\policies. Its as simple as that.

For more information see How to Implement the Central Store for Group Policy Admin Templates, Completely (Hint: Remove Those .ADM files!)