What's hard? Set up a server so you can create your own local domains and see what works and what breaks. There are a number of resources out there like the bind9 documents, and plenty of examples from places like stack exchange. Setting up basic domain records with NS and MX records is well documented, and even subdomains are straighforward. Once you have that much working then you can try adding more informational stuff like TXT and PTR records.

Don't forget to update your serial every time you make an update. The format isn't important as long as it makes sense to you, but you are limited to a maximum of 10 digits. You can do a straightforward date stamp like 20230729xx (leaving the last two digits for daily changes), you could do a unix timestamp, or you might have your own idea. However if you go backwards in your numbering then you have to wait for the expire time to run out before other servers will pick up your new record.

There's a huge amount of things you can do with dns records. My own setup involves two ISP connections and a custom root zone down to signed dnssec records. I literally have everything in place to run the whole internet using free software.