Sacrificing is the name of the game! An ideal first hand is two swamps and a mountain, or the black/red lands and a swamp, and a number of the 1 cmc cards. There are multiple strategies and synergies within the deck that make it really fun to play.
In terms of how to sacrifice you have the Ovens, Village Rites, Woe Strider, Ayara, Rankle and Fiend Artisan. The Ovens, Strider and Ayara can be used without mana to block a bigger creature with something weak and then still benefit from the action without spending anything, as this is slightly light on land, hence the Fabled Passages and combo lands. Despite that I've started games with just two lands in hand and still had a positive outcome.
A fun start I enjoy is having Claim the Firstborn and either an oven or village rites with a red and a black land available. Get your land out, then when the other player drops something on turn two or three, Claim it, attack with it, then sacrifice it - either for Food or for two more cards in your deck. Rinse and repeat if you get multiples and you can really stifle someone's early game decisions while benefiting yourself. This can continue to be useful through the game, especially if the opponent buffs cheap creatures - their buffs don't make them immune to Claim, and can make an awful lot of food if you have Ovens.
Kroxa is a fun starting card, drop him on turn two, get the opponent to burn a card from their hand and then if your sacrifices work well enough bring him out on turn six or seven and do some damage. This is also useful against Blue control although usually works better with some of the cards in the sideboard as well like Duress and Agonizing Remorse.
Archfiend's vessel is one of the most powerful cards in this deck and a starting hand, especially if you already have a resurrect. Attack, sacrifice it, then return it (ideally two) to the battlefield with Call of the Death-Dweller, kicked Nullpriest of Oblivion, Malakir Rebirth or Liliana (although those are rarer, but Malakir can also work as a land in a pinch), then when you rez it you have a 5/5 demon - hit that with Demonic Embrace if you have it and the game can end real quick. If things go well you end up with several 5/5 Demons and take out the opponent in a couple of turns.
Big things can mess you up, as well as blue control decks. The cavalry rides in with the form of Murderous Rider, letting you just straight up kill things no matter their power and then lifelink some health back. Bloodchief's Thirst can answer early threats cheaply and kill anything if you kick it, and Heartless Act can kill or weaken buffed creatures. And if things really go south - I'm looking at you, Scute Swarm - then you have Extinction Event to wipe the board. Also if you resurrect something like Serrated Scorpion with Death Dweller then you end up with a deathtouch, menace scorpion. And if things really go south you have Scourge of the Skyclaves, which can end up being double-digit power if you're low on health - especially when you kick him and halve the health of players.
Most creatures are cheap so they can be rez'd with Death Dweller and you can get two out, ideally Archfiend's Vessel but also the Scorpions, Ayara, Fiend Artisan and Scourge of the Skyclaves. Keep sacrificing for bonuses and then bringin' them back to do some damage. Remember that you can assign blockers, then before damage is dealt you can sacrifice for a benefit, which still blocks the creature (unless they have Trample). If Ayara is out and you resurrect you also do some damage - in one turn it's possible to drop two scorpions, get the opponent damage and health from ayara, sacrifice them with Ovens, then resurrect them and get the damage/health again - then eat the food.
The more expensive creatures have some good uses as well. Nighthawk Scavenger gets stronger the more you add to the opponent's graveyard and can give a lot of lifelink health while doing damage, and is cheap enough to resurrect with Death-Dweller. Rankle can absolutely ruin an opponent, making them discard cards (best used when your hand is empty), draw and lose health (great as a final move), make both of you sacrifice creatures (which you can usually bring back!) or any combination. If I have Rankle in my starting hand I usually keep him. Gray Merchant is great when you have a full battlefield to do some damage and gain some health, but even with minimal amounts of creatures on the field it still usually averages 3-6 damage/health regain. Liliana is good planeswalker for this deck, her +1 makes you both discard a card (try to discard something you can bring back later), her -3 gets more powerful the more creatures you've sacrificed, and her -7 is just excellent for this deck.
One of the weaknesses of this deck is that it has nothing to counter artifacts or enchantments. That's something I'm going to work on for the future, so against full sorcery decks you have to go really hard and aggressively.
