Ok, so I have decided to do a quick guide, so here it is.
When building a deck, you need to have a theme. Without a theme, you are, no doubt, going to have a pointless, dead-drawing deck.
If you left the game when it was in its early days and you have only just returned, there are no longer cookie cutter decks. What I mean by this is there are no decks in which you can throw the best cards around, into it and it will work.
With so many deck types around and more always coming out, it is hard to stick to one type of deck; I personally have multiple decks on the go at one time, using them depending on the surrounding and my feelings.
If you are unsure of what deck you want to play, then one of the best things you can do is use a site called 'Dueling Network'. This site is an online database in which it has every card in the game and is always updated. You can create a deck and play other people, random or friends and test out decks. This is one of the best tools around for a duelist; not only do you get to know your combos and how the deck works, you get use to how others duel against you and what counters your deck.
In the game of Yugioh, there are cards in which are called 'staples'. This simply means that these cards should be in EVERY SINGLE DECK THAT IS BUILT. They include cards, such as:
Post September 2011 Banlist
Monster:
Tour Guide of the Underworld
Spells:
Monster Reborn
Heavy Storm
Mystical Space Typhoon
Dark Hole
Trap:
Solemn Warning
Solemn Judgement
Extra Deck:
Black Rose Dragon
Brionac, Dragon of the Ice Barrier
Scrap Dragon
Stardust Dragon
Trishula, Dragon of the Ice Barrier
Ally of justice Catastor
These cards are the basic monster and back row killing cards that should be put into the deck, if not having some serious consideration.
There are many decks in the Yugioh world, but it boils down to Meta and Anti-Meta.
Meta: Meta Refers to the Deck(s) in current competitive use that are having the greatest succession in the professional play scene.
Anti-meta: An Anti-meta deck is any deck that is built to counteract the most popular decks being played.
That is it put in a nutshell. In a tournament, you will normally find 80%-90% of people running meta and the rest Anti-Meta. Why don't more people run Anti, I hear you ask. Because they aren't consistent enough. A good yugioh player will take into account their meta decks weaknesses and in the second round of duelling where siding is allowed, they will cover that weakness and render the deck helpless.
There is nothing stopping you making any deck that your heart desires. If you want to build that Batteryman OTK then go for it, but if you want to play in local tournaments or bigger events, then you are going to need to go with the popular, because it is popular for a reason.
Getting the balance of a deck is the most important thing. You can't just throw in all monsters, spells or traps, obviously there are exceptions, but only one or two decks at the most fall into this category. (Monster mash or Fuma FTK/OTK)
TEST TEST TEST!
You HAVE to test your deck in any way you can. Don't want to go on DN? That is fine, use real life friends. Don't have any around? Just use the deck against you. One way I test is by shuffling and playing as if someone was in front of me, guessing what will most likely happen, but this does take time to get right and you have to be very clued up on the meta to be able to do this. Just draw 5 then one for your turn and see what combos you can get going. If you have gone more than 2-3 attempts and not been able to pull off the deck/s combo, then you need to think about your deck and go back to the drawing board.
The main things that you need to know are the popular cards in the game today. If you know, you are blind-sighted in what combos will come your way and you have no hope in countering them.
Guess what your opponent is going to do, get inside their head, what would you do if you were them?
If your opponent doesn't do anything on their first turn, it is very likely they have Gorz or Tragoedia in their hand, so work around it, build up your defence or have a strategy if you are going to attack.
Don't be reckless, if you are reckless, you have already lost. The amount of times I have seen someone lose and beat someone because they get so excited that they are going to win, they miss the obvious counters that are there.
Yugioh is very expensive, everyone playing knows this. Your extra deck will cost you £100/$150 alone if you want the staple cards. So what are the expensive and cheap decks, but can hold their own? (Will be updated)
Expensive:
Plant decks
Rabbit Dino
Cheap:
Dark World
Six Samurai
OTK/FTK decks (Meaning One Turn Kill/First Turn Kill)
Yugioh is a game you have to spend time and money on if you want to play it as it should be. If you want to enjoy but don't want to spend money, stick to Dueling Network and the console games.
It is a game at the end of the day that it is fun. End off. ENJOY!