Welcome o the community, we are not many but we are very active.
Winter is comming so you better prepare by getting your dreamcast online and start having fun with us.
You should check the discord channel (the link is on the top right side of this forum) there you can ask short questions about getting online or arranging game sesions once you have everything set.
I personally don't have a GDEMU, but you are right, there is a loooooot of things you can do with it and this is a paradise of resurces for that and specially for asking questions about it too. I'm thinking on getting another dreamcast to have one with discs and another one with the GDEMU.
See you soon online!