pokemon card slowbro Dark (TR 12) - Team Rocket - English Colorless Retreat Cost Slowbro 020/078 - Pokemon Go

Boros is known for being very aggressive

The center of high-value candidates is the Manga Rare series Among items in standard commercial circulation, the cards that easily become candidates for high prices are, as expected, the Manga Rare series

Obviously these may be a miss for your format for other reasons (power, archetype mismatch, rarity, don't run planeswalkers etc) but here's a few that I found interesting, divided by broad category rather than color: While I'm still not done reading Cosima, God of the Voyage (I'm on chapter 2, the language is a bit dense) these cards are ones I do like both sides of

The dragon has a borderless foil version priced at around $16