You want something thats easy to identify as a proxy without ruining the play experience
Storage sanity: Deck boxes, binders, toploaders, and storage cases are built around standard trading card dimensions
If you want all the flashiest cards from the set, read on: 1
The only way to become the monarch, other than dealing damage to an existing monarch, is to play any of the cards that state you become the monarch like Thorn of the Black Rose or Crown-Hunter Hireling
The other ability, Team Tardis, lets you untap each creature you control with a counter on it at the beginning of your end step
Finally, do your market research