Here is my code for connecting an RFM95w Radio module to the Photon and then running the Radio Head Reliable Datagram Server and Client code on 2 separate Photon + RFM95w devices.
You can download the library and examples here: https://www.dropbox.com/sh/n3nrrkdkdlzp44o/AADgPVpiVZbS00wBB9LYv4hLa?dl=0
Then just open that folder using Particle DEV as shown below:
The Photon to RFM95W chip pin connection diagram is below:
I just used one of these Adafruit breakouts:
Amazon and Digikey have some in stock, Adafruit is currently sold out.
In good conditions, you can get 1-mile range with simple wire antennas in a suburban environment.
The other thread were we figured out how to make the Radio Head library work on the Photon is here: Particle Photon / Electron + RFN95W Long Range Radio