Slotting in Welcoming Vampire to replace Sporemound is a good choice, reducing the overall casting cost curve of your deck a little and replacing a card that relies on landfall triggers to be good, something the deck isnt optimized for
Cruelclaws Heist I must admit my bias here: Bloomburrow s Cruelclaw's Heist is one of my favorite Standard cards
March of the Machine, for instance, has tons of serialized cards, but its Collector Booster boxes are only $400
You can turn Treasure tokens (that Storm the Vault may have created) or Blood tokens into the 2/1 myr token that Brudiclad spawns
Oh and Vanquisher's Banner, Herald's Horn, all pretty deece tribal stuff
Long-game card-drawing advantage aside, Kefnet comes down early and, if set up properly, can deter people from attacking you for a good chunk of the game