Some of these cards may have price tags that are leagues above the rest, like For those that do spike in price, thats a function of the underlying utility of the card - not the collectibility of their category
Play this if you lack low drops, perhaps play it to compensate for being weak to ping effects or if you have a polar deck
You can start if you have a Namazu Merchant on the battlefield, at least 6 cards in your graveyard, and a total of 15 mana (Blue Blue Blue Blue Black Black Black Black and 7 colorless)
This means they can't be attacked by your rivals, essentially allowing you to earn points before retreating to safety
This build doesn't take budget into account and instead goes for sheer power and includes the most popular cards you'll typically see in an Ur-Dragon deck
This means you should always be able to play a useful card every turn