Welcome to modern! If you're new(ish) to the game, and have only played standard or casual games, you're in for a bit of a
shock. Modern has a much higher power level, and games are usually over by turn four (though it can end earlier or much later, depending on the decks). The format generally rewards proactive play, and especially as a new player, you want a something proactive and fast-ish. So I'll give you some overarching recommendations first, and get to your deck second.
First off, glad you asked about sideboarding, a *lot* of new players do not understand the importance of learning to sideboard. It is one of the most crucial skills you'll need to learn. You will play more games post board than you will with your original 60. I could spend all day writing about the practice of it, but thankfully there are several solid general guides on sideboarding (both construction and how to use them) on YouTube and Reddit. Save yourself some headaches and give them a read/listen.
Secondly, budgeting. This means different things to different people, but I'll assume you're coming in with a near-zero collection of cards. So a few tips to save you money:
- If you're new to the game and don't know what type of deck you'd like to play, try proxying a few of the top decks. With friends. You can get a better feel for the format, and see what you enjoy playing before you drop (potentially) hundreds or more dollars on a deck only to find out you hate playing it. Checking resources like mtggoldfish and mtgtop8 will give you a good idea of what is popular at the moment, though there is a lot of "fringe" decks that are played less, often a bit less competitive, but still capable of going 4-0 or however many rounds your FNMs go.
- If you find you want to buy into modern, invest in "staples" first. Sets of cards like
Lightning Bolt,
Path to Exile,
Fatal Push,
Serum Visions,
Faithless Looting, etc. will go a long way if you want to play a variety of decks.
- It's ok skimp a bit in the beginning. While some expensive cards have an effect that is completely unique, this is usually not the case. There is usually a less costly card that has about 80% the effectiveness. For example, compare
Thoughtseize,
Inquisition of Kozilek, and
Duress. TS is clearly the most powerful, but has the highest price tag. IoK cleanly sits in the middle, both in effectiveness and cost. If your budget is really hurting,
Duress is dirt cheap, but misses a lot of relevant targets.
Ok, now on to the deck you have built. This might get a bit harsh and
long. I will be explaining all potential card choices. And I will try to keep it under the cost of what you already have listed for the deck. If you want, just skip to the bottom for a list I would consider to keep the theme intact.
So, the overarching theme is sacrificing for value. That's awesome. It's a lot of fun, and I don't blame you for wanting to play it. But the deck you have built is reeeeeally slow for modern. You will likely just die a lot of times before you get your engine online. So we need to lower your mana curve, and look at your engine itself.
The first thing I am looking at is a few cards that do not contribute to your overall strategy.
Pyromancer's Goggles is painfully slow and doesn't have enough targets for its effect.
Nirkana Revenant is also slow as can be and doesn't really function as ramp.
Infernal Plunge is something we don't need the mana from if we build properly. Mogis, Tymaret, and Chandra are all more prison-oriented cards to grind someone down. They add very little to the deck. So we've barely started, and we have already freed up fourteen slots.
So we need some fast threats we can sacrifice over and over and some gods to get our value. You have
Nether Traitor and
Reassembling Skeleton listed, but I think there are a few better options. For the same cost (money-wise),
Bloodghast has one more power, can have haste, and doesn't take a mana to bring back to play.
Bloodsoaked Champion,
Gravecrawler, and
Gutterbones are both one drops, so that's a consideration.
Flamewake Phoenix is easy to trigger with gods in play. Haakon is more mana intensive, so I wouldn't really consider it. Erebos is very slow, costing a full mana more to play than Bontu. So he's out. Bontu I would up to three copies. Purphoros is solid and I could see keeping three copies.
Now we need a few ways to get our critters into the graveyard, and dig for our payoff cards.
Stitcher's Supplier is one mana to get up to six cards in the bin, which is solid.
Faithless Looting is known for enabling broken starts.
Cathartic Reunion is also a whole pile of value.
Cryptbreaker bins and gives us some board presence at the same time.
Removal is a really
simple one to upgrade.
Lightning bolt is extra reach, and just more efficient than
Abrade.
Lightning Axe bins a card and hits for 5, which is good if we have a recursion card stuck in our hand.
Fatal Push is just alright in this scenario, though we can very easily trigger revolt on it.
Sweltering Suns is actually the best sweeper for a deck that doesn't want its board
exile, so good pick, but I don't think we need one. Conflagerate is a solid option as you can play it from the bin.
Sideboarding in the current meta is a bit tricky, but I'll keep it cheap and as board as possible.
Grim Lavamancer is the one "expensive" card, but a total house against any go wide deck.
Tormod's Crypt is no
Leyline of the Void, but it exiles the opponent's yard and costs no mana.
Fatal Push and an additional
Lightning Bolt for more removal.
Sweltering Suns I put in the board as a two of, as a solid sweeper option. One
Shatterstorm for any artifact based decks, and three
Duress to deal with combo or control.
And here we have the end result:
https://deckstats.net/decks/64516/1264393-copy-of-necromantic-sacrifice/en