Gavin Verhey specifically stated multiple times in this announcement that a lot of the terms of these tiers fall under feel. It is technically very possible to build an incredibly powerful Commander deck that falls under the deck construction rules of the Exhibition Tier, but these decks are specifically weaker than the average Commander precon according to the second tier
Since you need to have a creature die in order for it to be exiled with a blood counter for Rayami, you might consider running Isochron Scepter and Flash
They are not useable again until they are readied again through an action or game rule, and are vulnerable to being challenged
Best for: anyone who plays at stores/events and wants a method that is both clean and rules-aligned
II, III Whenever you cast a spell this turn, put a +1/+1 counter on target creature you control
Contents: 1 ready-to-play deck of 100 Magic cards (2 Traditional Foil Legendary cards, 98 nonfoil cards)