That's right...two tribes in one!
Of the twenty-five Ally creatures in this deck, all but three also happen to be Humans. Which means that while Hada Freeblade is still an awesome one-drop, Champion of the Parish is just as good, giving you eight one-drops that can get absolutely huge.
Of course, most of these creatures can get beefy too: Kazandu Blademaster, Oran-Rief Survivalist, and Talus Paladin all get bigger for every Ally you play, and Adaptive Automaton makes them all even bigger. Then Primal Rage lets them trample over chump blockers and end things quickly.
The rest of the Allies do their own thing. You've got mass lifegain (Talus Paladin), ramp (Harabaz Druid), and flying (Avian Changeling, which counts as an Ally AND a Human to help your one-drops).
Ready keeps them alive, Descendants' Path keeps them cheap (and can frequently enable two Allies to enter play each turn), Cloudshift retriggers them.
And later in the game, when you could otherwise be running out of steam, Garruk and Doubling Chant can quickly restock you with several fresh Allies at once.
The sideboard has some off-the-wall includes, like easy creature kills--even of fatties--with Coordinated Barrage, the flexible Selesnya Charm, artifact control with Creeping Corrosion, artifact/enchantment hate with Devout Chaplain, and tribe/color protection with Kabira Evangel and Riders of Gavony.
I thought about splashing in red, but white and green seemed to offer plenty already. What do you think?
***Updates 3/25***
-2 Ondu Cleric, -1 Turntimber Ranger, -1 Cloudshift, -1 Plains, -1 Forest
+2 Mirror Entity, +1 Garruk, +1 Doubling Chant, +1 Godless Shrine, +1 Overgrown Tomb
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If you like Allies and Humans together, check out a much different take on the idea with a "darker" deck: http://www.mtgvault.com/jre47/decks/dark-human-alliance