Well… I guess advice for such an open ended inquiry is desgin our backup plan first and build around that.

Also decide what level of fault tolerance you want. If you want to be able to survive a disk failure without restoring from a backup then you’ll want at least a RAID1 configuration or similar.

If you do so be sure to test out your planned recovery methods before loading up all your data and thoroughly document your process so that when the worst happens all you need to do is follow your own directions.

The bare minimum is a hard drive and a computer. Unless you have a more specific question I’m not sure how else to answer. I don’t think I fully understand what your concerns are.

A server is quite literally just a computer. Your desires could be serviced by something as simple as a raspi with a USB attached external HDD.

My very first server many years ago was just a desktop chassis with old scrap parts I had lying around. If you don’t have parts on hand you can obviously buy them or if you are unsure about how committed you are to this project just pick up some cheap used system of Craigslist/some online marketplace/eBay/etc.

The above all assumes you are interested or comfortable with setting up the software side of things yourself. A prebuilt NAS device is again nothing more than a computer but among other things will come preloaded with an OS and software catered to fulfilling its role and typically making it highly user friendly to just start rolling with.

If cost savings is key though and you are interested in learning you can also just install Linux on any old box and set it up to do everything and more that a prebuilt NAS can.