There are a multitude of obstacles in the way of success in Magic. In Legacy, these obstacles are often outside the context of the mechanical problems and mistakes made during a game. You can - and believe me, many do - take yourself out of the running for Top 8 in your next event before you even Fork over your exorbitant entry fee. If you're looking to be the best, these are things you'll need to focus on. The good news is that they're relatively simple fixes compared to those mechanics I mentioned. Here are the Top 5 mistakes I see the collective Legacy player making before they sit down for round one.
1) You aren't playing blue cards.
In all likelihood, this isn't a hard-and-fast rule for your tournament to live and die by. Plenty of players get by on decks like Lands, Death and Taxes, Elves and...well I guess that's kind of it. The thing is, you can win with these non-blue decks, but you're crippling yourself in a significant way by choosing not to play blue.
Look, I understand the hate. Blue is the jerk color that gets to do everything, and usually at a fraction of the cost of the colors that are "supposed" to be able to do those things. On top of that, it's miserable to play against blue cards. They get to Nullify your spells (often for less mana than you pay for them), and they get both the best planeswalker of all time as well as the best draw spells and best creatures. With the fetch/dual manabase in Legacy, blue even gets easy access to things like burn, cheap removal, and fat creatures. Oh, and that same fetch/dual manabase just happens to play extremely well with Brainstorm, the best cantrip. The color can do it all, and that's not fair.
Here's the thing – no one said it was going to be fair. Do you know why decks like Delver and Stone-Blade keep winning tournaments? It's no secret – they play the best cards, and those cards are very often blue.
The Top 16 decks from the SCG Open in Washington, DC contain one Lands deck and two Death and Taxes. The other 13 are all blue in some fashion. Brainstorm is a busted card. Force of Will is a busted card. There is no argument about it. You are hobbling yourself by standing on shaky principles.
2) You aren't attacking.
Attacking means a lot of things beyond "turn a creature sideways in the Red Zone." Attacking can mean aggressively trying to assemble a combo, or pressuring your opponent via undercosted creatures, or casting Tendrils of Agony following a handful of other spells. What I really mean is being proactive. In a format with the average power level of Legacy, trying to play a pure control role through a tournament is like sticking your finger in the hole in the dyke. Eventually you'll run out of fingers and toes, and you're left looking foolish as the dam explodes. There are too many varied plans of attack, and trying to be the control deck or the prison deck will leave you weak to something. It's that whole "no wrong threats" thing cropping up again. Despite how devastating a Chalice of the Void on turn one may be, Abrupt Decay will still wreck your best laid plans.
I spent a long time in Legacy playing decks like Stax and Landstill. These decks were fine-to-good in a world where players weren't playing optimal lists and where the number of viable strategies in Legacy was simply much more limited. Dredge didn't exist. Storm combo was a joke. The best cheap creature to beat down with was Kird Ape. We've come a long way since those times, and the game has changed. Change with it.
3) You're on a budget.
Legacy is expensive. Hell, Magic is expensive. It's getting more so every day. At some point you will need to make the decision whether winning is worth the cost of the cards required to do it.
There are many resources out there for players on a budget, and there are many articles written about the best way to break into the format from a Standard or Modern vantage point. Unfortunately, when it comes down to it you're not playing on the same ball-field when you're limited by your budget. It's another unfair reality of the game. When scarcity is a factor and gameplay is a factor, the cards people want to put in their decks are the ones that will end up the most expensive. Usually that means the good cards. There's a reason Tarmogoyf is a $200 card and Troll Ascetic is a bulk rare.
There is absolutely nothing wrong with being on a limited Magic budget. There's nothing at all wrong with being conscious of the money you spend on your hobbies. Sometimes you can't have your cake and eat it too. If you have to ask yourself, "Is there a cheaper substitute for playing the deck/card I want to play?" you should really be asking yourself, "Is it worth it for me to play Legacy as opposed to another format right now?"
In the long run I would absolutely recommend every player get exposure to and experience in Legacy – but if your primary goal is winning, then enter the format at a pace that will allow you to satisfy the urge to win, rather than beat your head against the wall while you lose because of cards you can't afford.
4) You aren't net-decking.
The Magic culture surrounding the concept of net-decking is fascinating to me. Maybe it's because I'm one of those "old guys" who started playing Magic before the internet was really a widespread thing, but the fact that literally thousands or tens of thousands of people have already had the idea you had and have put effort into improving it is a GIANT BOON to me. When I started playing Magic, we didn't even know what all of the cards in a given set were, let alone have the fortune to have a million other people to bounce ideas off from.
The first constructed deck I built was a Faerie tribal deck built out of the back of a Scrye magazine. I had no idea what I was doing, but I did have a bunch of Scryb Sprites and a thirst for playing Magic. Someone out there was smarter than I was and put a bunch of cards into a deck that contained some synergy, and that was cool with me.
We've come a long way since Scrye and Inquest, but ultimately the story is the same. The idea that you have has probably been mined by someone or other out there in the inter-verse well before you made the connection. They likely posted on some forum somewhere detailing the process of testing that idea, and have gotten the input of someone else. Those people have probably done some work on optimizing their idea to make it streamlined for Legacy play. Then they either gave up on the idea or made it good enough to put up some results, causing others to notice, and subsequently net-deck their idea. So why try to reinvent the wheel?
There's room for creativity. I cut my teeth in Legacy as a frequent poster on mtgTheSource.com, where I was known for testing out off-the-wall ideas and failing with them time and again. Really, I've never met a convoluted combo I didn't love. To make matters worse, during the onset years of the Legacy format, the culture of the Legacy community was obsessed with credit for deck designs. Emrakul help you if you "stole" credit for a deck that was created by someone else – I was just as guilty of this miserable habit as anyone, and have the internet history to prove it. As someone known for my love of all combos terrible, my reputation was largely dependent on the performance of my last creation, and having other people succeed with those decks and be given credit for them was a huge blow to my ego; and let's be clear here, ego is the real driving force behind the anti-net deck mentality. You don't just want to win, you want to win "with my own creation." You think that playing with a deck someone else designed somehow takes away from the Purity of the win. As they say, you don't get four match points for winning with a deck you designed.
I was a victim of this mentality for a long time. It took me years to see that the collective effort of the world of Magic players had far more processing power than I could muster myself. Eventually, when it comes time for real tournaments with real prizes on the line, I learned to leave well enough alone, pick up a tried and tested deck, and pick up the free wins along the way. It's fine to be creative, and expressing yourself through your deckbuilding is a fantastic outlet for many Magic players – but if your goal is the trophy at the end of the weekend, you have to realize that you can't do it on your own. Even Conley Woods, widely held in highest regard for his unique perspective on deckbuilding, saw significant improvement in his results when he finally set down the binder full of pet cards and picked up the best deck.
5) You aren't playing Legacy.
It's been a long time since Goblins was a good deck. It's been a while since anyone won with Zoo. Enchantress comes and goes, but for the most part the deck is dead. Legacy was, at one time, a paradise for brewers who wanted to make a push with their favorite deck. Once upon a time, it was a wide-open metagame where anything can and did win, and you were just as likely to see a player at the top tables with a Moat in play as you were a player with a Dark Confidant. Those times have come and gone.
Legacy has a clear and established metagame. The saturation of events coming from the Star City Open series, and now the Premiere IQ series, has allowed the cream to rise to the top, and demonstrate that, when a week-in week-out series tests the format over time, you will have a set of decks that simply outperform the rest. Delver of Secrets is the defining creature in the format. Omni-Tell is crushing events. Stoneforge Mystic is still an efficient way to apply pressure in a control shell. Putting a Griselbrand into play on the cheap is still a thing. These are extremely efficient and powerful strategies that are going way over the top of the kind of things we used to see in Legacy. Your Cleric Infinite Life combo deck from 2003 probably can't compete with the level of cards that are premium in Legacy today. And I don't think it's unreasonable to expect that kind of power barrier in a format with ten thousand legal cards. Are some things prohibitively powerful? Perhaps. But the powers-that-be have made it pretty clear that they're satisfied with the format's shape today, so I wouldn't expect much to change in the near future –and whatever changes there may be, I doubt they'll be enough to Foster the triumphant return of Deadguy Ale. Sorry.
I know this comes across as harsh. With all of these hard lessons in a row it sounds a lot like I'm saying "conform or be left behind," and to some degree that's true. Once upon a time, Legacy was more Commander and less Standard, but the truth is that the days of that environment are gone. You can still find bastions of the old Legacy in LGS's across the world, but if your focus is competition and winning prizes, you can't compromise on these points. Which is not to say that winning should be your only goal, or that it's somehow a nobler goal than others. The important thing is to really honestly define your objectives to yourself, and work toward them with abandon. If that means you want to ignore my advice to eschew a self-built deck then so be it – but do so with the acknowledgment that you're playing on "hard mode." If you can live with it, so can I – but you're taking the burden of you bad beats by a net-deck story unto yourself. Don't say I didn't warn you.