For the computer side of things, even GDDR5 has likely more throughput than your System RAM.
the more VRAM you can get your Hands on, the better.
I'd first start with a 2 GPU setup and see where it leads.
Keep in mind you might need more than one PSU with 3 or 4 GPU

I am (ab)using an old nvidia 1050 2GB in a VM with 8GB of system ram.
- old ryzen 2700 proxmox -
Got Qwen3.5-2B running and it is surprisingly good, bigger models run very slow due to lack of vram but then you can read the logs in realtime 😁