How to Build a Beginner Yu Gi Oh! Deck

Know the rules of Yu-Gi-Oh. If you aren't very familiar with them, keep the guidebook close by to refer to when you duel or build a deck.

Pick a theme for your deck (i.e. Elemental HEROs, Dinosaur, Pyro, Exodia). Decks focused around a central archetype or theme will be more consistent and have access to good support, making you more likely to win. Do research to see what kinds of cards are good, or try to find cards you have lying around that work with each other. You won't be able to use archetypes, or cards with the same names, right off the bat, but you can use cards centered around an attribute or type, like "Allure of Darkness" or "Onslaught of the Fire Kings" to support a deck with a majority of monsters of one attribute or otherwise. Also keep in mind that some cards, like "Mystical Space Typhoon" or "Raigeki" can be used in every deck with success.

Find the cards you need. Look through your collection and pick out cards belonging to or supporting your archetype, or research good cards online. If you need, buy or trade for some cards.

Pick some monster cards (around 15-20) that correlate with your deck theme. (i.e. Dinosaur monsters for a dinosaur deck.) Use effect monsters with helpful effects, such as Man-Eater Bug and Neo-Spacian Grand Mole, as well as some with good attack. Good attack stats for monsters below level 4 are 1600-1800, monsters level 5-6 should have at least 2300, and ones with levels 7 or higher should have at least 2500. Don't include more than 4 or 5 high level monsters in your deck, unless you can reliably special summon them. Also, remember that attack points are not everything. A weak monster can have devastating effects, and a powerful monster could be easily destroyed by a spell or trap.

Pick spell cards (10-15 cards) that correlate with your deck theme. Ensure you pick power-ups for your type of monster. If you don't have a specific type, then choose general ones. You should have good sources of spell/trap destruction, monster destruction, searching, and summoning.

Pick trap cards (8-12 cards) that will help you. It may be harder to find trap cards that support your deck, so you can just go for generic traps. You should have good sources of attack protection, effect negation, summon negation, and/or spell/trap negation, depending on your deck type.

Build an Extra Deck. The Extra deck can contain up to 15 cards, and you should fill it if possible. Add your archetype support cards, then get good generic Xyz monsters. They will work in almost any deck, as long as you have at least 3 monsters of the same level. Include Synchro monsters if you have a tuner. Fusion monsters are for more specialized decks.

If you're building this deck for tournaments, you'll want a side deck. A side deck consists of up to 15 cards which are kept separate from your main deck. Between each duel in a Match (best out of three duels) you can swap cards between your Side and Main/Extra deck, depending on what you are facing. Side in cards that will help a lot against certain matchups, but are too situational to put in your Main deck. If you aren't planning to play in tournaments, you won't need to build a side deck.

Review your deck and see if it fits well. Make sure all the cards work well together and you will not get too many dead draws. Try it out against a friend in a duel to see how it runs. If there are cards that help a lot, try to maximize them while cutting out unhelpful, hard-to-use cards.