If you're starting from scratch and have a requirement for other less tech-literate family members to use the device, I'd typically advise to start off with an appliance like a Synology. Myself, I started with QNAP which tend to have better hardware but questionable firmware. Once setup the other users didn't even need to know what it was or how it worked. Probably go with a mid-range 4-bay device. NASCompares and SpaceRex YouTube channels can provide reviews and comparisons as well as examples of what device in what tier.

Once you have a device up and running you can explore your needs over time as things mature. Do you want to run other services? What's your rate of storage growth? etc etc.

If you happen to have spare hardware just laying around that could be used in a self-build then by all means have a crack and setup a trial system. If you need to buy disks then that doesn't matter as you'll need them for an appliance anyway - just look at compatibility first (WD Red Plus, Seagate IronWolf etc) and make sure they're CMR not SMR.

If I were starting out now I'd have a play with Xpenology (to see if you'd like what Synology offers), Open Media Vault, Unraid, and TrueNAS Scale. These systems are so much more usable than when I started this journey over 20 years ago. It'll be all good.