What you want for ram, and what the pc needs for ram are 2 different things.
For the master, 8Gb. Minimum of 4Gb per VM. It's not so much the loads or 'heavy lifting', it's the combinations. You have OS, back and forth communications, apps etc.
You'll run into serious issues if trying to balance running multiple VMs and sharing threads. Figure a minimum of 1 thread per VM, preferably 2 threads. So you'd be looking at a 6c/12t, not a Pentium.
I'd suggest a Ryzen 2600/2700x, not the 3 series versions. With the 3's, Ryzen switched to preferred core status, which can impact high thread usage at constant rates.