TCGPlayer works if you're already deep in that ecosystem, but it's not where we'd start for graded cards specifically
The Lost Caverns of Ixalan - popular with players who like dinosaurs, artifacts, explore-style adventure themes and fun chase cards
If you have any kind of board presence when Sliver Legion comes out to play, it's going to have a Craterhoof Behemoth-type impact on the game, and probably end it that turn
Kaalia is an aggro deck that wants to attack frequently so it can cheat massive flying beaters into play, along with a few strong Demon creatures on the ground
Upheaval, Gifts Ungiven, Yawgmoth's Will, Balance (the most ironically named unfair card), Wheel of Fortune, Gaea's Cradle, Tolarian Academy, Survival of the Fittest (a classic combo with Recurring Nightmare), Vedalken Shackles
Use Misty to get some Energy acceleration going and Leaf to Bench Druddigon when Gyarados is ready