Top 10 list (summary with prices TCGplayer market) 14: Three Tree City variants Three Tree City (Borderless winter) $35.62 Three Tree City (Borderless other seasons) up to ~$27$35 Three Tree City (Normal border) $19.56 Why its valuable: land synergy with creature-type strategies makes it playable in multiple formats, and the seasonal borderless art is collectible
And one of the most crucial is selecting the right card leading card

Advanced Search Sets Random Syntax Aboroth Ageless Entity Ancient Greenwarden Animar, Soul of Elements Arboretum Elemental Ashaya, Soul of the Wild Avatar of Growth Avenger of Zendikar Averna, the Chaos Bloom Awakened Skyclave Bane of Progress Barishi Barkweave Crusher Blanchwood Prowler Bloodbriar Bloom Hulk Botanical Brawler Bramble Creeper Bramble Elemental Bramble Familiar Bramblesnap Brambleweft Behemoth Briarhorn Brokkos, Apex of Forever Brokkos, Apex of Forever Brushfire Elemental Carnivorous Moss-Beast Cavalier of Thorns Child of Gaea Chlorophant Cloudthresher Conifer Strider Cosmogoyf Creeperhulk Creeping Trailblazer Cytoplast Root-Kin Cytospawn Shambler Diamond Weapon Doomgape Earthquake Dragon Elderwood Scion Embodiment of Insight Endurance Evercoat Ursine Eyes of the Wisent Fecund Greenshell Fertilid Floral Spuzzem Flourishing Bloom-Kin Force of Nature Force of Savagery Forgotten Ancient Foundation Breaker Fungus Elemental Fusion Elemental Gaea's Protector Gaea's Revenge Galewind Moose Glade Watcher Grave Sifter Greensleeves, Maro-Sorcerer Greenwarden of Murasa Groundbreaker Grove Rumbler Guardian of Vitu-Ghazi Guardian of the Great Conduit Healer of the Glade Heartmender Hivespine Wolverine Hollowhenge Scavenger Horde of Notions Humbler of Mortals

I don't love everything or even most things about the finance aspect of the game, but again, it's not like most of the forgeries going around are the $2,000 Reserved List cards that were bought out by speculators
5 Madame Null, Power Broker Legendary Creature Madame Null, Power Broker is a three-mana 1/3 legendary creature with deathtouch, but more importantly, whenever a creature you control enters, you may pay life equal to its power to place that many +1/+1 tokens on it