If you are completely new, I would recommend a Synology. Very easy to use.
datahoarder
Who are we?
We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
We are one. We are legion. And we're trying really hard not to forget.
-- 5-4-3-2-1-bang from this thread
If you truely want to do one from scratch truenas I think is the goto project, (I personally go with pre-built solutions of external HDD or Synology/QNAP NAS).
YouTube is your friend. So is piracy. And torrents. And a must, get cheap HDD's.
Why cheap hdds and not ssds?
SSDs are unnecessarily expensive when you're looking at hoarding dozens or hundreds of terabytes of data. You won't be gaming off your drives you use for hoardings so there's really little benefit except in transferring stuff off them. Most of what people hoard tends to be media or documents which are find being played directly off even a slow modern HDD.
HDDs are cheaper than SSDs per GB
Shuckable HDDs are even cheaper per GB
I've purchased several 18TB WD Red Pro HDDs for $249.37, or $13.85/TB. I've also purchased and price tracked shuckable HDDs and don't recall ever finding a better $/TB than that.