Hello.
I bought LoRa on Aliexpress, specifically Heltec V3. It comes with a wire as an antenna and a simple case, which is sufficient for a dense network, but I recommend purchasing a better antenna and filter for 868 MHz. I'm not sure if Meshtastic's website directly sells LoRa, probably not.
The question is whether to choose Meshtastic or Meshcore. We from Omega were setting up the Meshtastic network last year, but this year we all gradually switched to Meshcore and covered almost the entire Bratislava. Some people remained on Meshtastic, but honestly, I don't know how it is there now.
Regarding firmware, the latest stable version is recommended.
There are communities of people using Meshtastic, or Meshcore (or other derivatives) on social networks, so it's not difficult to come across people who can help or advise.