You can easily cut the Human / Shark subtheme (and use the partners to build another deck), which mostly feels forced in with the primary Gavi cycling plan to give the deck more new legendary creatures
Howling Mine (T1, Ext, S) If any one card in Magic is the poster-child for card drawing, it is Howling Mine
by exiling it while its still on the stack
Its a little expensive, but if youre in a heavy noncreature deck, its full of value and doesnt die to a Wrath of God like Talrand, Sky Summoner does
You can also do it after declaring attacks if you want to just throw your smaller creatures to a certain doom when you dont have any good attacks
While it was never determined who was the original owner of this card when it was sold for $65,000, its most likely one from the VGC tournaments