Among the many fanciful creatures and variety of magics found on Eldraine, those of the green-aligned cards can place themselves at the top of the food chain
The important tip to remember for making these higher mana costs cards playable is to manipulate your deck composition and synergies in Constructed formats
Buying a pre-made deck, editing it slightly at first, and then finally building decks from scratch, is the general way to advance as a player
Goblins, humans, and warriors look doable, and you could probably cross creature types (e.g goblin rabblemaster)
While I personally only sell via Buy It Nows (while making liberal use of the Send offer to buyers feature), sometimes you just need the cash fast and thats perfectly okay
Ariel, Sonic Warrior Enchanted ($400) By far the most highly sought after cards in any Disney Lorcana set are the cards at Enchanted Rare level