You lose out on some good options by not having access to green, but there are some great white and Azorius merfolk youll have access to
In a deck that plays a lot of high-mana cards you get a good amount of value per card in hand for this, and it works especially well with the 4-power draw effects as you can churn through the deck
That said, most playgroups are perfectly fine with using proxies
While a 3/2 for four mana isnt great, the ability to counter a wide range of effects (spells, activated abilities and triggered abilities) or destroy a creature or planeswalker when Ertai enters makes this card an amazing Swiss Army knife that can answer a number of kill-on-sight threats, often in a surprising way, as the fact that this card counters triggered abilities can really stymy a foes game plan in unexpected ways
These 100 cards include your decks commander (more on that in the next section)
The Black Gate The Black Gate is a nice utility land that can help you to attack a player freely if they have the most life