Deck Building 101
Around 30% to 60% of a match is already determined by the quality of construction of your deck. This article focuses on the basic elements of deck construction. We all should know that you must have 60 cards and no more then 4 of the same cards, with the exception of basic energy cards.
There are basically two types of decks. They are the mono/single color decks and the two color decks. There are very few 3 or more color decks that perform well, so those will be avoided here. I consider a single color deck having 1 type of energy, and a two color deck having two types of energy, regardless of the types of Pokemon. Having more then two types of energy (not including double colorless energy cards) generally make it difficult to get the energy you need.
Single color decks are quite often the simplest types, although sometimes they are some of the strongest. When creating a single colored deck, you should keep in mind offense and defense. Offense is your Pokemon's ability to attack. Because of that, all Fighting or all Psychic decks should be avoided. There are too many Pokemons resistant to either Fighting or Psychic. You could add Colorless Pokemon to the mix, but if the bulk of your Pokemon are Fighting/Psychic, you'll have a terrible time. I was play testing Snorlax one time, and it generally sucked, but I've never seen it woop so much ass when playing against this mono-Psychic deck. Also, there are a few Pokemons with resistance to Lightning, but all of them are weak to Leaf. So mainly Lightning Pokemons with 4 Scythers should do well.
You should keep in mind defense as well. An all Fire deck is generally weak because all Fire Pokemons, with the exception of Moltres, are weak to Water. The two best types of single color decks are Water and Plant. Water decks have ole mighty Blastoise to back them up, and Gyrados for sacrificial firepower. This works out well because Blastoise has a weakness to Lightning and Gyrados has a weakness to Leaf. Plant Pokemons are similar in that some are weak to Fire and some are weak to Psychic.
Two color decks require a bit of planning. Each color should work to compliment each other. Generally you should choose a color that's strong against the weakness of your other color. For example, Water and Fighting go well with each other because your Water is weak to Lightning which in turn is weak to your Fighting. Water and Plant go well because your Plant is weak to Fire which is weak to your Water. Colorless Pokemon and Scyther go well to assist in meeting this goal. Scyther provides a strong offense against some Fighting and Water Pokemon as well as a resistance to Fighting Pokemon. Colorless Pokemon provide resistance to Psychic and Fighting Pokemon.
A simple Color wheel is shown below. The color after the one listed is generally weak against it. Most of the time (there are exceptions), you should choose two colors that are one color away from each other. For example, Lightning and Fire go well because your Fire is weak to Water which is generally weak to your Lightning.
Psychic Fighting Lightning Water Fire Plant Fighting Colorless Psychic Plant Water
It may seem like a simple task, but choosing your deck colors is a very important decision. Whether you decide to go with a single color or a two color deck is mainly your decision. Raindance decks have proven the power of single color decks and the Haymakers have proven the two color decks.