Myself i'm running a instance for two people in a pretty small lxc container on my home server- 1vCore, 512MB of ram and 8GB storage. Currently it utilize around 5% of CPU, ~250MB of ram (+260MB of swap), and ~2GB of storage (nearly 50/50 picts/postgres), in terms of network traffic i see average of 20kb/s, depends how many communities are you subscribed for.
My homeserver is running on i3-4150, 16GB ram and a couple of ssds, using Proxmox VE as hypervisor
edit: typo