Hey folks! Yarium here. I was going to post a giant deck-building guide for new players for Sealed, but it was ginormous. Here's the trimmed down post!
#1 - What is Sealed?Magic is a really interesting game because of all the ways you can play it. Sealed is a format that is played at every Prerelease and Release of a new set, and it's a great way to start jumping in. You'll receive 6 packs of cards, plus a foil rare (and in some formats, a unique pack of on-colour cards), and you build a minimum 40 card deck using those contents, plus using any basic lands you want. Your goal is to create a deck that will go through 4 or more rounds of play to win it all!
#2 - What makes a good Sealed Deck?A good Sealed deck will consist of between 22-24 of your best cards, plus 16-18 lands. For your first games, stick to this, and don't go over 40 cards. You want your BEST cards all the time, and if you put in more cards, you actually reduce the chances of seeing them. Ideally, you want to be in 2 colours, but there's times when you'll go into three. Finally, you want your deck to have a an overall strategy for winning.
#3 - What Strategies Win?There are 3 main kinds of strategy; Aggro, Mid-Range, and Control. Aggro is when you put all the mana-cheap cards in your deck and try to win before your opponent even plays anything of consequence. You must win fast, because it won't take long for your opponent's cards to start dealing with multiples of your cards. Your best cards are cheap creatures with high power, and damage spells that hurt or cause life loss to your opponent (Example:
Ahn-Crop Crasher). You'll need some way of getting the last few points of damage in.
Control is when you put more mana-costly cards in your deck so that your cards will be very hard to deal with (requiring multiples of your opponent's cards), while having lots of removal spells and creatures with high defence so that you don't die too early. Control decks are some of the hardest to build in Sealed, because they require a specific mix of the right costly cards, and the right removal. Your best cards are hard-to-answer bombs that can win the game on their own late into the game (Example:
Scaled Behemoth). You'll probably need some card draw to make sure you have enough "gas" to survive to the end where these cards can shine.
Mid-Range is between these two, and is often built by having a mix of cheap cards to come down early and put pressure on your opponent, and some big stuff late to close out the game. Most Sealed decks will be this. You switch between offence and defence as necessary, often dealing big "chunks" of damage at a time before switching gears again. Evasion is great for this, as it helps to put a "clock" on your opponent. Your best cards are ones that are strong by themselves, but reinforce all of your earlier plays (Example:
Decimator Beetle).
#4 - What are my Best Cards?Your Best Cards are the ones that have the highest impact for the least cost. 1 damage for 10 mana would be too little impact for too much cost, and 10 damage for 1 mana would be an insanely high impact for very little cost. The impact that a card has can be guessed in "floors" and "ceilings". The "floor" is the worst-case scenario for a card, and the "ceiling" is the best case. Cards that have high floors and low ceilings are often way better than cards with high ceilings and low floors. For example,
Haze of Pollen is fantastic when it works, but most of the time it's a dead card in your hand.
Ornery Kudu is never fantastic when it works, but it works all the time, no matter what. As such, Ornery Kudu tends to be a way better card than Haze of Pollen.
Outside of that, your Best Cards are the ones that match your strategy most. Haze of Pollen might work better in a green Aggro deck, where you can make that "ceiling" happen more often against other Aggro decks when in a race, but is a terrible card for Control, where it'll almost always end up as "3 mana, draw 1".
#5 - How do I put this all together?Take all your cards, and sort them into piles based on their color. Put aside any cards that are low impact, or that have low floors, into a junk pile. Only touch this junk pile at the end if you're struggling for a few more cards. Then take the two biggest piles and look through them together to see if there's an apparent strategy to them. If there isn't, switch one color for another and look again. If there is, take out cards that don't fit this strategy. Remember that some colorless cards work great in different strategies.
If you have more than 24 cards at this point, cut again, removing the cards with the lowest "floor". If you're under 22 cards (which often is the case), start looking at the junk pile to see if any of them match your strategy. Once you have between 22-24 cards, sort these cards by their "expected mana cost". Some cards cost more or less in different situations, and some have alternate costs, like cycling. Aggro decks should have most of its cards in the 1-3 mana range, with only a few 4 or 5 cost cards. Control should have most of its cards in the 3-5 mana range, with only a few 1 or 2 cost cards. Mid-range should have most of its cards in the 2-4 mana range, with only one 1 cost card, and a few 5-7 cost cards.
Lastly, add your land. Usually it's a good idea to have the same percentage of lands as you have colors; so if your deck is about 50/50 on colors, it should be about 50/50 on those lands too. If all your cheap stuff is one color, give that color a higher percentage of lands.
#6 - Wrapping it all upQ: When do I splash?
A: You don't. You're new to the game right now. However, if you really need to, you only "splash" for one or two cards in another color that are just PERFECT for your deck, and they should be good later in the game since you likely won't have both that card and its associated land early on. Aggro decks should avoid splashing like the plague. You want at least 3 sources of mana for that colour, even if that source is a land that "filters" mana for it.
Q: Should I go first or second?
A: Go first. There honestly are good time to go second, but like splashing, you're not ready for that yet. However, Control decks like going second some of the time because the advantage of the "extra draw" is best for them. But you don't know how to best use that advantage yet, so really, don't do it.
Q: What do I sideboard?
A: Your sideboard is all the cards that you didn't use when building your deck. You might realize that there was a better card for your deck after your first game, so bring it in by taking another card from your deck out. Always look at the sideboard! Sometimes your opponent's strategy will make one of those cards much better.
Q: Should I run more than 40 cards?
A: No. No no no. Definitely not. Even the pros debate whether it
ever is good for one of their decks to be 41 cards rather than 40, and they get the most mileage out of that. Doesn't matter how good some other card is, it's either in your 40, or it isn't. You put in more, and you make it less likely to ever draw the cards you really need. So don't. And while we're on that topic, don't go below 16 lands either to squeeze something in. Even the most aggressive decks shouldn't do this, even in the hands of a pro, and a pro you ain't (yet). Your deck really should be 17 lands and 23 other cards. Control tends to be a bit higher, some of the time (18 lands, 22 other, so they more often get to the land counts they need for their higher cost stuff), and Aggro decks tend to be less (16 lands, 24 other, because they don't need lands too much after the 3rd or 4th one). You'll almost definitely be Mid-Range, which just loves that 17-23 split, so just go with that for now.
Q: How do I play?
A: Too big. Research more articles online. However, never be afraid to ask for advice after a game! Your win-loss ratio and prizes are based not just on how well you did, but on how well the opponents you faced did. Win or lose, you want your opponents to do really well in all their subsequent games! So ask away.