I do like U/G Merfolks chances on becoming a breakout deck after Rivals of Ixalan releases, but Kumena, Tyrant of Orazca isnt the reason why and I expect it to be a small role player in the strategy with little chance for overlap into other strategies
Take a look at some of these early examples: Chaos Orb : Just look at that floating brain
Alrund's Epiphany A common companion of Goldspan Dragon, Alrund's Epiphany is that most hated of cards: the extra turn spell
It's great as card flow in any aggressive or midrange tribal brew, and it has enhanced value with graveyard recursion in Black like Living Death or Patriarch's Bidding
These effects are commonly tied to enters abilities (see: Fleshbag Marauder) but the edict effect can be tied to upkeep triggers, attack triggers, even activated abilities
The autotapper isnt perfect, though , and once in a while it messes up, but while you learn the game the auto-tapper makes things faster and easier