Chapter 5: Item builds
One of the key skills needed to playing League of Legends is to know what items to build. In this chapter I will go over the key and situational items that can be bought by each role described in my role guide which can be found here, http://howdoiplaythisgame.blogspot.com/2013/10/league-of-legends-roles.html.
Section 1: The Ad carry
The items for the ad carry are usually very generic and do not differ much until you get to your 6th item. At the very beginning of the game most ad carries will start of with a Doran's Blade to provide a slight hp boost and sustain within the lane. The ad carries will usually build Berserker's Greaves for boots and will differ after this purchase. If the Ad carry focuses more on right clicks ,Such as Tristana and Caitlyn, rather than on Ad scalings on their abilities, such as Graves and Sivir, then they will rush an Infinity Edge over a Bloodthirster which you should buy if you have high ad scalings on your abilities. There is one exception to this rule and that is Vaynes should usually rush a Blade of the Ruined King to provide kiting potential and a decent slow. Infinity Edge provides huge amounts of Dps, or Damage per second, while Bloodthirster provides more Ad and valuable lifesteal. After your first core item you usually want to get the item that you did not pick up. After this item most Ad carries will go for a Phantom Dancer to further increase their attack speed and provide extra critical chance that synergizes well with the Infinity Edge. Some Ad carries that split push a lot can buy a Statikk Shiv to further increase their push potential. After these items the Ad carry wants to buy a Last Whisper to increase your damage against high armor targets. The 6th item is where the build varies depending on your play style and the enemy team. If the enemy has a lot of cc then you might want to buy a Mercurial Scimitar to provide a decent amount of magic resistance and a cleanse on an item. Another decent item is a Banshee's Veil which not only provides magic resistance and hp but a spell shield that refreshes every couple of seconds that is useful against poke compositions. The final option is an Guardian Angel which gives you a revive at significantly less hp on a 5 minute cooldown. Other notable items that can be bought on an Ad carry are Trinity Force, Black Cleaver, and Zephyr.
Section 2: The Jungler
The Jungler has so much versatility in item builds that it is hard to designate a section to them. Instead I will give items that every jungler should have and items for specific jungle categories. Junglers should start out with Hunter's Machete to provide extra damage against neutral minions and 5 health potions for sustain in the jungle. With this machete the jungler can build a Spirit Stone for some sort of sustain or a Madred's Razor for faster clear. On Tanky junglers you want to build your Spirirt Stone into a Spirit of the Ancient Golem to provide tenacity. Along with the spirit item you might want to buy Randuin's Omen, Locket of Iron Solari, Frozen Heart, Spirit Visage, Bashee's Veil, or a Sunfire Cape depending on the situation at hand. For Carry junglers of for damage in general you might want to build a Ravenous Hydra, Blade of the Ruined King, Bloodthirster, Trinity Force, Iceborn Gauntlet, or a Frozen Mallet.
Section 3: The Top Laner
Much like the jungler the top laner is too versatile to make a definitive item build. The top laner requires the most skill in determining what to build because not only do you have to build to counter your opponent but also you have to build to counter the enemy team. Due to the nature of top lane I will list generic items to build against certain enemy match-ups. Your item build in top lane varies greatly from each game so it is up to you to decide what you should build. Starting item builds can consist of a Doran's Shield or Blade, Boots, Cloth Armor and 5 health potions, or Rejuventaion beads and a couple of wards. Against Ad oriented top lanes you will want to usually build Ninja Tabis for boots and some sort of armor item such as a Sunfire Cape or Randuin's Omen. Against more Ap oriented top laners you might want to build Mercury Treads for magic resistance and additional tenacity. Also you can build an Abyssal Scepter or a Banshee's Veil. ONLY BUILD THESE ITEMS IF YOUR CHARACTER SYNERGIZES WELL WITH IT. For example, if your character has no Ap scaling whatsoever then it is not wise to build an Abyssal Scepter for magic resistance when you can just build a Mercury Treads.
Section 4: The Support
As stated previously in my other guide, Supports need to help the team and build some items to help with the low gold income. To help support your team, supports should start off with a some sort of combination including a Faerie Charm, Vision Wards, Sight Wards, and various potions. The Faerie Charm should be turned into a Philosopher's Stone at the earliest time possible to help with your gold intake. After your Philo Stone you can either build another gold item in the form of Kage's Lucky Pick or just rush basic boots. You should be buying wards every single time you go back to base to make sure that your lane is always warded and if you can try to buy Vision wards to counter the enemy Sight Wards. After your basic Boots you want to rush into a Ruby Sightstone for more wards and some hp. After the Sightstone you can start to build items to help support your team such as Mikael's Crucible or Shurelia's Reverie. Also if nobody on your team can make a Locket of Iron Solari then you should. Throughout the game you should also be buying ORacle's to deward key objectives and make sure your wards stay up Since they get next to no farm it is not uncommon for supports to have 1 or 2 major items by the end of the game. Some other decent support items can be Stark's Fervor, Twin Shadows, or Shard of True Ice if you manage to get a decent amount of farm.
Section 5: The Mid Laner
Since most Mid Laners tend to be Ap bursters I will focus on what to build for said bursters. To start off you should got to lane with either a Crystalline Flask and a couple of health potions for sustain, a Doran's Ring and 2 health potions for more Ap, or Boots and 4 health potions to dodge the skillshots of certain champions. After your starting item build you can build a couple more Doran's Rings if you are facing an aggressive Jungler or Mid Laner to help boost your health. After your starting items you can start building a myriad of items. For more Damage you can go Rabadon's Deathcap, Rod of Ages, Void Staff, Deathfire Grasp, Athene's Unholy Grail, Archangel's Staff Liandry's Torment, Lich Bane, or Morellonomicon. For more defensive purposes you can build an Abyssal Scepter, Zhonya's Hourglass, Rylai's Crystal Scepter, Guardian Angel, or Banshee's Veil.
After you get full item's you should not forget to buy the Elixirs to further increase your damage. Also Twin Shadow's and Eleisa's Miracle are the best items in the game.
/sarcasm