Dear Taylor, Its the thought that counts, and your thoughtfulness shines through with this gift
For that of course the Ceremonial Duel Deck was probably the best candidate for this, taking under consideration the famous cards that go in triads (Magnet Warriors and the Three Knights
A card like Cathars' Crusade, while absolutely disgusting (in a bad way) for bookkeeping purposes, really likes Felisa's token production because it means more counters, which might mean, in the future, more tokens
While you wont have as many Supporters in a deck as the other card types, the ones you do have often give you the best advantages
In other cases, cards rise in price thanks to rumor, hype, combo potential (that is often unrealized), or simply a changing metagame
That's counting every unique card in every mainline and special set released since 1999, including Secret Rares (but excluding holo and reverse holo variants)