Cards like Hades, Lord of the Underworld and Part of Your World bring characters from the discard pile back into the hand, while Mickey Mouse, Wayward Sorcerer can keep flooding the field with Magic Brooms
It's an excellent answer to an opposing combo, and circumvents most counterspells since your opponents can't cast anything in response
The field notes cards remind me of the schematic cards from the Brothers War expansion
Sources: Heritage Auctions, PSA Grading Scale
If you try to do neither, youre basically asking for a marked-card problem
As long as you have all your most valuable stuff in one little pile/binder, it makes it easy for people to give you better offers and you also hopefully know enough that you didnt leave 300$ cards sitting in bulk boxes