The first involves expectations around the game, mainly focused on deck contents, types of win conditions, and gameplay
Token generators like Rhys the Redeemed, March of the Multitudes, Secure the Wastes and Aura Mutation will be ideal in an Aragorn and Arwen deck
There may be no good answer here
For example, starting with a two-drop Ichor Wellspring you can get a three-drop like Chromatic Lantern if you need to smooth your mana or a combo piece like Ashnod's Altar or Phyrexian Altar or Crucible of Worlds
There are a number of cards you can't use in Explorer: Expressive Iteration Field of the Dead Geological Appraiser Karn, the Great Creator Kethis, the Hidden Hand Leyline of Abundance Lurrus of the Dream-Den Nexus of Fate Oko, Thief of Crowns Once Upon a Time Teferi, Time Raveler Tibalt's Trickery Underworld Breach Uro, Titan of Nature's Wrath Veil of Summer Wilderness Reclamation Winota, Joiner of Forces MTG Alchemy banlist Alchemy is another digital format for MTG Arena, which is based on the Standard card pool