My collegue actually runs on 16G, but he has to consider memory when starting a VM, but it's doable.
You can run on 8G, but it wouldn't be a good daily driver. But maybe if you have a very specific purpose?
24G+ is comfortable. I'm currently at 48G and have 43G "mapped" to VMs. It's very easy to use a lot of RAM!
edit: maybe i'm being a bit optimistic for sys-net, which is the vm hosting the driver for the network card: these drivers are included in the linux tree and would need to be extracted and packaged into an unikernel. But for every non-driver vm it "should be easy" to get an unikernel implementation (drivers for paravirtual devices are easy to write).