The biggest thing about SAN is you are now handling block storage instead of file, so there are some logical and workflow differences you need to wrap your head around.
You can share these volumes over iscsi (ethernet) or fibre channel quite easily, but most people use iscsi because it is really easy to put it on its own subnet/VLAN on your existing switch to get it running as opposed to buying FC cards and a separate switch.
You should really always keep iscsi on its own VLAN to keep other network traffic from destroying your performance...
If you are just mucking about I would suggest just getting a couple of SSD and an optiplex sff for cheap.
Software you could start with the SolarWinds san as it is pretty easy to set up.
If you want to keep a San as a purpose built device, definitely look into ESOS (enterprise storage os) as it supports a lot of hardware (nvme) and is capable of scaling up to enterprise levels.
You also don't need an absurd amount of hardware for a San... You might be raising the bar if you want nvme but you need very little ram and basically just a relatively modern cpu.
Read up on a few of these blog posts on the hardware he deploys to test ESOS and you'll get some comparison points. https://marcitland.blogspot.com/2017/05/millions-of-iops-with-esos-nvme.html?m=1