Hi Jonathan,
it seems that you already have most parts running and only a few things are missing...
In principle, there are different solutions possible and sometimes "best practice" is a question of personal favorites. I assume that you have an Arduino (or similar) that is aquiring different data and sending a kind of data stream to the Raspberry Pi on a regular basis.
For example the Arduino board measures a voltage in mV, a pressure in mBar and a temperature in 1/10 degrees. These values are then sent in a serial protocol to the Raspberry Pi board, e.g. "Axxxx - Bxxxx - Cxxxx;" On the Raspberry Pi board you can receive and analyze the protocol and assign the received values to properties of the GUI application.
Let me refer to the article Assign variables from Hardware to GUI - it describes exactly how to get the data from UART and how to provide it to the GUI application.
I think this will answer your questions. If there is still something missing, please let us know.
Happy coding!
Manfred.