Anyways, so to the new players out there the question seems to be, "How does I build deck?", and the answer is really simple, "Anyway you want to." There are some simple guidelines to follow, otherwise whenever you play you might find that your deck has no focus, it isn't consistent, or it has mana problems. You could always go and look up actual championship decks that have been play-tested, but you may not enjoy that play style, or be able to afford some of the pricey cards tournament champions tend to have. So the solution? Create your own masterpiece.
Deck construction starts by first picking either a color, a theme, or a card, and every deck has to have a minimum of 60 cards (With the maximum being as many cards as you can humanly shuffle without help from another person). You could start by picking a color, which usually picks your theme as well. For example, green magic has many creatures and creature improvement spells so you might make a deck with lots of strong creatures and pack spells that make 'em even stronger.
You could also pick a theme, or a mechanic that your deck works with. A life gain deck could use white spells that gain life, or black spells that steal life, or both. Sometimes if you find a card that you just fell in love with you can easily build around it, such as the card Artillerize, which can work great in a deck that uses its graveyard as a resource or is based on sacrifice.
After you have assembled your crew of cards the next issue to discuss is the land issue. Now the usual rule is to have at least a 2/5 proportion of land to other cards in your deck, which comes out to around 24 lands for a 60 card deck. This ratio is good, but it really comes down to how much mana your deck really needs. If the general mana cost for everything in your deck is 3 then you could exclude some lands and go with an 18-20 land deck. But know the more mana you exclude, the lower your chances are of drawing mana when you play.
Another thing to consider is using multiple colors in your deck. It is easy get mana-screwed as you add more colors to your deck, so when thinking about splashing some of that red in your blue deck, consider using some non-basic lands that can provide two colors, or other land replacement cards such as Llanowar Elves or Manaliths that can provide mana but aren't lands themselves.
Anyways, hopefully you all found this guide helpful in any way, shape or form and I wish you all happy deck-building!
