TL;DR Direct answer : The best Sapphire cards from Fabled to prioritize are Hades - Infernal Schemer, Aurora - Dreaming Guardian, Dig a Little Deeper, Mulan - Considerate Diplomat, and Cruella De Vil - Style Icon
For example, if you control The Ozolith ("Whenever a creature you control leaves the battlefield, if it had counters on it, put those counters on The Ozolith.") when Zack Fair's last ability resolves, you'll put the appropriate number of each kind of counter onto both The Ozolith and the target creature
Although the deck list above pictures this card in its Iconic form, luckily you wont have to purchase one of the most expensive Whispers in the Well cards to build this deck, as this guy is relatively affordable via my partners at TCGPlayer
We asked ourselves: How would Stitch react to this setting
But, it's also worth noting that prices change all the time, so some cards may change in value closer to release