One of the easiest places to start is with All is Dust, but a case can also be made for now slotting Hibernation, Riptide, and Wash Out in as well
The stock list is filled with all these cute little synergies which add depth and complexity to the list -- cast two spells per turn, legendary creatures matter, tokens matter -- but Y'shtola is very clear on what she wants to be doing, and that's chaining together high mv noncreature spells, and this deck simply refuses to do that
In a nutshell then I think we need more cheap cards, more card quality, more removal and more things to challenge some of the staples
15x Magic: The Gathering cards
This card is basically Flame Slash, Lava Spike and Faithless Looting rolled into one