What should I do with an extra 500gb SSD

Hi level1Techs
I have a question on pools. I have a New Setup for TrueNas Scale on an old system running
i7 7700k
16gb ram
EVGA 1080ti
3 x 4tb HDDs
2x 500gb ( one set up as boot and one extra)
since its only one drive of 500gb left I was thinking about using it as cache drive but I’m wondering if it would be better served as Metadata or Log VDEV.
Ill be using the NAS as JellyFin Server. maybe ill throw in a couple extra sticks of Ram to play more with some VMs. I had an unraid server before but thought it would be a good idea to switch since I plan to one day mess around with a cluster setup. Any recommended changes or upgrades? Maybe point me in a good direction on some reading materiel’s since I noticed I might have to learn some commend line?