Ironically, right before this article was published, The one-of-one serialized Ring was confirmed to have been found, so this isnt a realistic thing you can open anymore
To figure this out, you need to think about what's going to matter in this game as a whole, as well as ask some questions about what you know of your own deck
Classics mass pumps like Moonshaker Cavalry and Craterhoof Behemoth turn your many 1/1 creatures into a winning attack

(Bevy of Beebles) Basri Ket Basri, Devoted Paladin Calix, Destiny's Hand Chandra Ablaze Chandra Nalaar Chandra, Acolyte of Flame Chandra, Awakened Inferno Chandra, Bold Pyromancer Chandra, Dressed to Kill Chandra, Fire Artisan Chandra, Flame's Catalyst Chandra, Flame's Fury Chandra, Flamecaller Chandra, Flameshaper Chandra, Heart of Fire Chandra, Hope's Beacon Chandra, Legacy of Fire Chandra, Novice Pyromancer Chandra, Pyrogenius Chandra, Pyromaster Chandra, Roaring Flame Chandra, Spark Hunter Chandra, Torch of Defiance Chandra, the Firebrand Comet, Stellar Pup Commodore Guff Dack Fayden Dakkon, Shadow Slayer Daretti, Ingenious Iconoclast Daretti, Scrap Savant Davriel, Rogue Shadowmage Dihada, Binder of Wills Domri Rade Domri, Anarch of Bolas Domri, Chaos Bringer Domri, City Smasher Dovin Baan Dovin, Architect of Law Dovin, Grand Arbiter Dovin, Hand of Control Ellywick Tumblestrum
This is very frustrating
As we get into Rare and Super Rare the ink cost can be up to 8, with a larger amount of cards having two or three effects