This deck focuses on hitting hard and fast with the Marauder being a potential finisher. It also features a decent uncommon in Lightning Berserker and an interesting rare card in Foul Renewal.
Here's the deck list:
2 Lightning Berserker
2 Kolaghan Aspirant
3 Kolaghan Skirmisher
2 Kolaghan Forerunners
2 Screamreach Brawler
2 Ambuscade Shaman
2 Sprinting Warbrute
1 Boltwing Marauder
2 Swift Warkite
2 Tormenting Voice
1 Foul-Tongue Shriek
2 Twin Bolt
1 Foul-Tongue Invocation
1 Foul Renewal
1 Vial of Dragonfire
1 Kolaghan Monument
2 Impact Tremors
1 Evolving Wilds
Let's take a look at the heart of this deck, which is the cover card, Boltwing Marauder. He costs 3BR (3 colorless, 1 Black, 1 Red) to cast and is a 5/4 flyer. Whenever another creature enters the field under your control, you can give a target creature +2/+0 until end of turn. With the amount of creatures in this deck, especially with them often returning to your hand if you use their Dash abilities, you're often going to use this ability on the Marauder itself to swing for a lot of damage in the air.
The main issue with Swift Warkite is that you're going to want to play this before combat for that haste to be relevant. It has an okay synergy with the Ambuscade Shaman or Boltwing Marauder, but 6 mana is a lot to invest to get essentially one free Dash.
Overall, the synergy of the creatures in this deck is pretty good. The Dash mechanic is well-represented, and there are enough other creatures with Dash in the Tarkir block that could easily supplement this deck: Mardu Shadowspear and Mardu Strike Leader in Black and Mardu Scout and Goblin Heelcutter in Red are excellent candidates to upgrade the creature lineup.
The Warkites are probably best replaced by a couple copies of one of those other Dash creatures. Flamerush Rider is another creature you could consider, as it can make a token of your best attacking creature. That token entering the battlefield also has great synergy with the Marauder and Shamans, as well. Another card to consider would be Brutal Warchief, which fits well in this attack-happy deck, and has the added benefit of paying 3RR to choose how your opponent's creatures block.
Kolaghan Skirmisher is a fairly vanilla 2/2 for 1B, but it does have a Dash cost of 2B. They're not too exciting. Kolaghan Aspirant is a worse version of an older card called Ashmouth Hound; whenever it becomes blocked, it deals 1 damage to that creature. The Hound could deal 1 damage if it were to block itself, as well. It's not terrible, though.
Kolaghan Forerunners is actually a pretty decent Dash creature. It costs 2R to cast and also has a 2R Dash cost. The Forerunners always have 3 toughness and Trample, but its power is decided by how many creatures you control, making it much better as the game goes along. It also has solid synergy with the Marauder, as its damage is a lot harder to block due to the trample.
Screamreach Brawler is pretty unexciting as a 2/3 for 2R, but it also has a Dash cost of 1R, which makes it okay for purposes of this Intro Pack.
Warbringer is extremely effective in a deck like this, as it reduces Dash casting costs by 2 colorless mana. A 3/3 for 3R isn't too exciting, but it also has a 2R Dash cost. However, it's worth playing it for its regular cost just to keep it on board to get the Skirmishers, Forerunners, and Brawlers on the board with dash for only a single colored mana.
Sprinting Warbrute is a 5/4 for 4R that has to attack every turn if able, but has a Dash cost of 3R. With Warbringer, that Dash cost is only 1R.
The non-creature spells are rounded out with the obligatory Monument and Vial of Dragonfire. In this case, the monument is of Kolaghan, which serves as both a mana rock for Red and Black mana and providing an opportunity to create a 4/4 flying Dragon. The Vial of Dragonfire is an expensive Shock. You'd be better off replacing both with copies of Wild Slash or Lightning Strike.
Also, as is usually the case with Intro Packs, the mana base has 25 land in order to guarantee hitting your land drops. A full playset of Bloodstained Mire - the red/black fetchland - would allow you to drop this land count to 23 or 24 to make the deck a bit more consistent.
All told, there's a decent basis for a very playable Dash-centered deck. As the creatures that would complement and improve this deck aren't incredibly expensive, this Intro Pack looks to be a pretty good buy. Keep in mind that while there are synergies that are fairly effective in the deck, it probably won't be the shell of a future tier-one deck. It will be at the very least fairly fun and consistent, however.
As usual, Intro Packs tend to have rather strange combinations of non-creature spells. In this case, this non-creature lineup is headlined by Foul Renewal. It serves as both a way to return a creature to your hand and also a sort of removal. It gives a target creature -X/-X where X is the toughness of the creature you got back from the graveyard. Whether or not that's worth 4 mana is hard to say, but as removal in an Intro Pack. it's not too bad.
Twin Bolt is decent enough removal for the early game. Tormenting Voice gives you two cards at the cost of 1R and having to discard a card. Impact Tremors is an interesting enchantment that deals 1 damage to each opponent whenever a creature enters the field under your control. Flatten is a bit costly at 3B, but gives a target creature -4/-4. Defeat only destroys a creature with power 2 or less. Foul-Tongue Invocation forces your opponent to sacrifice a creature, and if you reveal a Dragon from your hand as you cast it or control a Dragon already, you get to gain 4 life out of it. There's also a random copy of Duress thrown in.