I read about a Rally the Ancestors deck that was maybe 4 colors and used green to ramp and to dump cards into the graveyard, and then used Rally to create some mega ETB chains. Here I submit a Mardu RtA deck that uses Butcher of the Horde to get around RtA not granting haste. Like most of my decks, I haven't actually built or played this.
Goal 1: Build a Standard deck for under $20 (mid) using only Tarkir block so that cards don't rotate out soon.
Goal 2: Create some crazy shenanigans with Rally the Ancestors and Butcher of the Horde.
The key creature is Butcher. You probably aren't going to win with all the other junk, so the plan involves getting a BotH out and giving him haste and lifelink to pound the opponent.
The other creatures are all focused on either feeding BotH or helping you stay alive.
RtA is there to let you bring all the junk back at the best moment for a blast of ETB and dies effects, and to feed the Butcher.
Open with a tapped land if possible. There are no 1-drops, but you want good work in turns 2 - 4, preferably with a Butcher attacking unblocked at the end of the open. And you're going to need all 3 colors of mana, but one red source will cover you for the whole game.
Example good open:
1. Land
2. Land, Cleric, gain 3 life.
3. Land, Sibsig Icebreaker, discard a Merciless Executioner (opponent discards also).
4. Land, Butcher, sacrifice both creatures for haste and lifelink. Attack for 5.
5. Land, Attack, RtA for 3. ME sacrifices itself and opponent sacrifices a creature. Gain 3 life. Both discard. Sacrifice Cleric or SI for lifelink. The other one can either be used for vigilance or saved for a blocker on opponent's turn (make sure to sacrifice it before your turn so it isn't exiled).
At this point if all has gone well, you've attacked for at least 10 and gained 16 life.
Very similar results can be achieved with almost any combination of the 2-drop and 3-drop creatures. Aside from Butcher, Alesha is the only creature you really want to keep on the field. She gives you a mini RtA each turn she attacks, and it pairs nicely with Butcher if you can use her to return a Cleric, SI, Sultai Emissary, or Sandsteppe Outcast. Everything other than BotH and Alesha can go to the GY to fuel RtA.
Some creatures you shouldn't even try to cast. Use SI to get your extra 2- and 3-drops into the graveyard, and use ME as a Diabolic Edict if needed. Emissary should be played and sacrificed as much as possible because it gives you card advantage and more than 50% of your deck is creatures.
If your Butcher dies, you're in luck -- RtA can bring it back (for an expensive 6) and it can give itself haste, lifelink, even vigilance if you need it to block (and if you're lucky, it will die and not be exiled). Remember, RtA lasts until your next upkeep, so you can use it for blockers even if you cast it on your own turn. And as long as you have at least one Butcher who isn't an Ancestor, you can sacrifice everything else to avoid exile.
We spent almost 1/4 of our budget on Sidisi and Anafenza, and they both play special roles. Sidisi gives you an extra shot at your key cards and she is the only big body other than BotH. She's expensive to RtA but so so worth it if the game goes long. Anafenza is good at making your crappy creatures better, but she can also buff the hell out of Butcher if you RtA. Just makes sure you put all the bolsters on the stack first and sacrifice any non-attacking, non-Ancestor creatures before bolster resolves. Generally you'll want all those counters on Butcher for max lifelink, but in some cases it's ok to drop some on Alesha, spirit token, etc.
RtA can create complicated situations with the stack, so think them through and don't miss any triggers. If you have a Grim Haruspex in the mix, sacrifice it after other things so you get your card draws. It's ok to draw past 7 cards if you're so lucky -- any creatures you discard make your next RtA even bigger. If you get draws and discards (SI) in the same RtA, put them in whatever order helps you most. And of course, any ETB during RtA requiring a sacrifice should sacrifice itself unless you can get more immediate value by sacrificing an Emissary. Remember that spirit tokens and manifests you get during the RtA are not temporary, so you don't have to sacrifice them if you don't want to. And since RtA is an instant, judge carefully whether you're best casting it before combat or before or after blockers are declared.
Jeskai Barricade is a tricky card. It can help you avoid losing a key creature. It can put RtA or a key land back in your hand if you accidentally manifest one. And during RtA it can put one of your ETB creatures in hand to be cast again later. Don't just play it straight unless you are desperate for the blocking.
You won't always draw BotH or RtA, but there are synergies in the other cards that should help keep you alive a while. SI will usually hurt your opponent more than you, unless he or she is also playing a graveyard strategy.
In the sideboard, Minister of Pain replaces ME if you're facing tokens or weenies. Duress helps if you fear counterspells. Abzan Advantage helps against enchantment combo decks. Impact Tremors gives you an alternate way to win if you can't get your attacks through, or if your opponent is effective at killing/exiling BotH.