Obtaining Flair for a card will consume some of your duplicates, depending on the cards rarity, and you must have at least two cards left, so you will need multiple copies of a card you want to obtain Flair for
The List Before I dust off the crystal ball, first I want to make sure we distinguish between oddball cards with unique effects and cards that are far too complex or narrow to see legitimate playever
Notable Cards: Reprints and $$ Scions & Spellcraft has five cards in the $2-5 range, three in the $5-10 range, and two notable money cards above $10
So theyre not expensive to pick up these days, despite their age
The severity of this question varies with Bounty conditions, current (and future) Level, and what sort of Commander decks your opponents are playing