Heres my shortlist of noteworthy upgrade options, divided by price point rather than card function: $1 OR LESS OPTIONS Marionette Master, Armix, Filigree Thrasher, Gravebreaker Lamia, Disciple of the Vault, Voltaic Construct, Ill-Gotten Gains, Stinkweed Imp, Orbs of Warding, Silent Gravestone, Scourge of Nel Toth, Mimic Vat $10 OR LESS OPTIONS Priest of Yawgmoth, Staff of Domination, Crypt of Agadeem, Pili-Pala, Basalt Monolith, Bolass Citadel, Metalwork Colossus, Nettlecyst, Currency Converter, Grim Hireling, Ruthless Technomancer MORE THAN $10 OPTIONS Entomb, Reanimate, Altar of the Brood, Retrofitter Foundry, Cabal Coffers, Defense Grid, Blightsteel Colossus, Darksteel Forge, Revel in Riches, Pitiless Plunderer THEY PUT THE NASTY IN DYNASTY This precon has been one of the hardest to make upgrade recommendations for not because theres any shortage of good options, but because theres just too many equally strong directions to take the deck

Id love one for my Commander deck, but not at this price, sadly
But in a game with plenty of spellslinging, River Songs Diary will be giving you a free spell every turn for very little initial investment.
Theyre excellent for three color decks, and if you still need to pick some up for yours, now might be a great time