This deck is one I've been debating on for a while. I love Eldrazi but I have struggled to find a build I really liked for this tribal type of deck until now.
I looked in to what I feel gives the best success against the popular decks in the format. Many deck run Planeswalkers, Ramp for a big Ulamog, Control (usually with Black, White, or both), G/W Tokens, and the obvious Bant Company (gag!)
To combat Planeswalkers we are running Counters, we know when walkers are coming with certain decks so we prep ourselves and crush their spirit. We also have a Thought-Knot Seer exile to get rid of pesty walkers or dangerous creatures. So we have to be ready to have something that can kill them or be ready to counter. We use this same idea to stop Ulamog Decks.
With Control I love Eldrazi's matchup. Exiling gets every creature in standard but there aren't very many Exile cards in standard so we look at the most popular removal, Black. Grasp, Path, Price, and the oh so hated Languish are all so destructive. To combat this we are running Tide Drifter and Always Watching to boost cards like Eldrazi Displacer, Thought-Knot Seer, and Reality Smasher making them (possibly) out of range for Grasp of Darkness and Languish. These cards also have a really sweet interaction with Eldrazi Mimic because as creatures enter they are instantly boosted by Drifter and Always Watching.
Say you have a Mimic, Drifter and Always Watching on the battlefield going into turn 5. If you were to play your land and cast a 5/5 Reality Smasher it would enter as a 6/7. So Mimic would become a 6/7, the get the boost from AW and Drifter becoming a 7/9. This can become Dangerous early game.
As well all Eldrazi are free from Ultimate Price which makes Ruinous Path or To the Slaughter (or other sac cards) the only cards that can remove our bigger Eldrazi.
Against G/W Tokens we have to attack the Planeswalkers and make sure to always be ready for a secure the wastes. We make sure to attack Gideon with Stasis Snares as they try to swing with him. Counters and TKS exile is always an option. Don't forget Relfecto Mage can bounce tokens and we can start removing them with Eldrazi Displacer too (Great for Hangarback Walker).
Oh Bant Company... For this I feel like our sideboard is our best way to win. We have Relector Mage to Bounce, Counters and TKS to stop a CoCo, Hallowed Moonlight in the Sideboard to destroy them as they come in, Talent of the Telepath to possibly use it a CoCo against them since we are heavy in the 3 drop spot as well, and Declaration in Stone to get rid of multiples like Sylvan Advocate.
Synergy
We have pretty good synergy in this deck because of Mimic, TKS, and Smasher but having the ability to control with Eldrazi Displacer is what helps most. He becomes a target for early removal helping our other creatures stay alive, can blink their creatures to free up an attacker, blink Reflector Mage to Bounce, blink TKS to exile or Smasher to make Mimic Huge. Don't forget you can blink a blocker after they are declared a blocker to get the block and save your creature.
Smasher/Mimic Combos Show
Smasher/Mimic Combos can do a lot but I think the biggest one would be to block with both and blink Smasher after declaring his block, possibly killing an attacker, the making Mimic a 5/5 or bigger possibly killing another attacker when they thought you didn't have the power to do so.