All strategy should be able to be summed up concisely, otherwise you have no clear goal. The strategy of this deck is simple
-- Overwhelm the Enemy with big creatures --
with this goal in mind, this deck created for standard takes two planeswalkers as the lynchpin to the strategy
Xenagos, The Reveler - Capable of generating creatures in a pinch to defend himself and give me space, and generate mana otherwise. the large amount of mana he can generate the longer the game goes on will become extremely intimidating, our goal is to get as many creatures onto the field as possible with this in mind.
Garruk, Caller of Beasts - What good is mana if we cannot spend it? While Xenagos' ultimate will accelerate us greatly, allowing us to both ramp and gain free creatures, we need a reliable way of getting more cards into our hand. Garruk is the perfect synergy for this strategy, allowing us to fill our hand with cards we can play, and every new creature on the field allows us to accelerate our mana even further so we can play MORE! His second will allow us to play some of our creatures early in a pinch, but i find this to be almost useless in this deck. Finally, his ultimate allows us to throw down some of our best creatures no matter where they are in our deck, truly a good acceleration and fitting our mission statement.
From my opening hand, i want to get down as many lands as possible, due to the fact that we have no turn one plays, take a dual land over a normal land. Red over the other colours, as our red is exclusively locked up in dual lands (16 of them however, we will never want for red mana). Prioritise playing of caryatids for more mana, and fleecemane lions. Fleecemane is very cost effective, two mana for a 3/3, and later on if it survives into our mid to late game we can buff it further, which also helps us create a very very hard to remove source of mana, AND defender for xenagos.
as a side note of a potential weakness, it is truly best to gain access to the hydras of this deck by drawing them, naturally or with garruk, as they both come in as 0/0 and draw their power based on the mana pumped into them, while this gives us a great way to attack (and combo with trample), putting htem onto the battlefield via xenagos or garruk's spells will result in a 0/0 that will be removed immediately as it has 0 toughness.
however, they are effective to play in the mid and late game, as you can play them with a conservative amount early on, but later you can truly pump huge amounts of mana into them to take the win as soon as possible. mistcutter hydra is especially effective at this, with protection from blue and haste, a huge mistcutter could take hte game from a player who spends too much mana and has no response to its arrival.
--For those of you with more money, or better collections than I, please substitute the guildgates with Sacred Foundry and Stomping Ground, they're the same thing, but can come in untapped at the cost of 2 life, its a much more effective version of hte same card, but coming in at around 30 times its price (in this country at least)--
I hope you all enjoy this deck and my write up on it, i came up with it from some research on Gruul cards, and from my own mind. i started by examining the theros scrylands and realising Gruul was strong. i have only began playing recently, and i aim to collect this deck within a month or two.