Typically they fix mana which has given you some quality but they also thin your deck
Knowing which cards are valuable, in what grades, from which sets, requires serious study
You can turn your entire board into huge threats in a pinch if you have the mana for it
Charizard Gold Star, Pikachu Gold Star, and Rayquaza Gold Star are the most sought after
Creature - Wizard Otter Draw (CTRL to add secondary) Evasion Bria, Riptide Rogue Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.) Other creatures you control have prowess
Pokemon (Promo) $52.28 A Cheeky Lugia Appearance The most valuable entry commands a massive lead over its competition, more than doubling its next closest competitor's value