I found the easiest way to know what I've got was just to collect 4 of everything.
For making decks, I rely on my huge brain.
Ok, so I don't have playsets of Hunters (Rares), Rise of Saruman (C/UC/R), or
Treachery &
Deceit (C/UC/R), but there probably aren't many who do.
It's been so long since I've actually made a new deck that I just don't remember. I probably put it together during the days of LotR Online in that program, then got the cards from my collection and sleeved them.