As with any IT project, your first step is to define your requirements. What’s the real justification for this? For me, it was monitoring temperatures and my heating system. Avoiding a very expensive repair after a frozen pipe easily justifies the cost and effort.
Once you address your primary issues, you can add other features just for fun. But be careful. Every feature, function, protocol, integration, automation and device type you add will add to the maintenance overhead and increase the number of breaking changes introduced with each version.
There’s a lot of good advice in this thread: