VLAN tagging / trunk ports and at least 16 ports (layer 2 is fine).
Nothing too fancy (so no Cisco 3750G suggestions here lol) .. To give you an idea - at the moment I am using for this setup 2xDS108 from Netgear so you get the idea what I mean with cheap and cheerful

I know I won't get them for 20 bucks, but I also don't want to pay 100s .. is that even possible ?
Oh and to make matters worse, needs to be as small as possible so I doubt even an old cisco switch would do tbh.