Writing a page means editing a file with a simple syntax like markdown (called gemtext).
Running a gemini server is about as difficult as running a file sharing client.
There are pre-built server packages as part of Debian and its derivatives.
Or, one can install Rust and download and build the agate server. That's what I did on my Raspberry Pi B. That Raspberry has an Ethernet port and USB port which can power it from my FritzBox. Needs half a Watt of Power when idle. Then, one needs to start the server on bootup. This is done via a service file for systemd.