Dredge is a mechanic unlike any else. Along with storm, it is one of the only 3 (banding being the other one) mechanics ranking 10 on the storm scale. And for good reason; dredge allow for massive card advantage for zero cost and is often painted as the bogeyman of formats such as legacy.
But why play it in modern? Because it is fun, complex, powerful, and unexpected.
Although dredge has been putting up respectable results lately, you will have a hard time finding hate against it. In fact, you will most likely only run into living end hate (if anything) when playing against most decks.
But anyway, down to the primer.
Starting off it's important to know that there are a plethora of ways to play dredge, with the two broadest being Dredge and Dredgevine. In this primer I will only talk about dredge, as dredgevine plays differently, and is the subject for a different primer.
There happen to be a few variations on dredge at this point. You have more classic dredge, where sheer mass of creatures straight from the yard is important, and bridge dredge, which gets Bridge from Below into the yard, and uses sac outlets to overpower the board. First I will start with classic dredge.
Drawing cards, discarding cards
Draw spells are good for getting extra dredges, and dredging earlier.
Insolent Neonate is the gold standard. It dredges first turn, and gets value off bridge every once in a while.
Faithless Looting formerly the best option, it still has its fans, as dredging twice, and discarding twice for one mana is good. It also has flashback.
Dangerous Wager
is also commonly seen as a two of, because it dredges on the same turn as faithless, but you get to discard your hand.
Conflagrate
kills it value-wise; for two mana, you get to deal a ton of damage, and discard your hand. It serves the same position as Firestorm in legacy.
Other popular options include
Goblin Lore
and
Burning Inquiry
.
Gettin' cards in the yard:
To make sure you get enough cards into your graveyard, you want to run between 8 and 16 dredge cards (not including Dakmor Salvage)
You will almost always run playsets of both Golgari Grave-Troll and Stinkweed Imp. As you add more dredge you get to Golgari Thug, and Life from the Loam which both serve different purposes.
Dakmor Salvage doesn't really fit in this category, as it's value is less for getting lots of cards into your graveyard, but rather getting a land back easily.
Creatures
Narcomoeba: flies, is free, chump blocks well with bridge, slam dunk for almost every deck.
Bloodghast: another auto include. Comes back for free off lands, can get in there with haste late game off a Dakmor Salvage. Value!
Prized Amalgam: there is no way I can fully express how much I love this card. It comes back free off narc, bloodghast, or any other play you will probably make. The end of the auto includes.
Gravecrawler: all you need is one Prized Amalgam and you're in business. This card is great for aggressive go wide decks.
Stitchwing Skaab: What! Why play such jank? Although it seems bad at first this card is almost straight upside. 3 power flier? Check. Discard outlet? Check. Turns on Gravecrawler and gets back Prized? You got it.
