My take on Merfolk in standard. Pump up the team, card advantage and evasive.
Need to figure out sideboard still.
Creatures
Kumenas Speaker: One drop that easily becomes a 2/2.
Edit Added Mist-Cloaked Herald. U for a 1/1 unblockable feel like I needed another one drop to stay aggressive.
Merfolk Branchwalker: Two drop that explores. Card advantage
Merfolk Mistbinder: Two drop lord.Pumps up the team.
Silvergill Adept: Two mana draws a card when it enters battlefield.That card draw keeps the train rolling
Jadelight Ranger: Three drop that explores twice. Card advantage
Vineshaper Mystic: Three mana and it pumps up two Merfolk.
Forerunner of the heralds: Four mana and when it enters you search your deck for a Merfolk to put on top of the deck. This guy pumps itself up every time a Merfolk hits the field. Very good if youre missing that extra pump from a lord or if your board is built up and you need tempest or herald.
Herald of Secret Streams: 4 mana and all creatures with +1 counters on them cant be blocked.
Hadana's Climb: It's 1GU gives another +1/+1 at beginning of combat. When there's 3 or more counters it flips to the land. Tap the land pay 1UG and target creature gets +x/+x where x is it's power. Doubles the damage on a creature. Easy flip, still testing with it.
Enter the unknown: One mana and target creature explores also you can play additional land. That mana ramp helps a lot and card advantage.