QEMU-KVM how much memory to allocate. cores, disk for VM:?

Question

KVM

Hi all!
The question is ripe,
there is a server with CentOS (64 RAM, 1TB, CPU 12), on it is a virtual machine (QEMU, LIBVIRT) Win2012R2, how much to allocate to this virtual machine?
Provided that she alone will spin there, nothing will be installed except for her.

I didn’t find anything on the Internet, except for the -balloon (ballooning KVM) driver, which sets the range (for example, from 16GB to 32GB)
But how to run it and attach it to the VM? (also didn't find anything)