The Learn to League Items Guide: Part II

Lich Bane - 3470g
+350 Mana +80 Ability Power +30 Magic Resist +7% Movement Speed UNIQUE Passive: 100% chance when an ability is used that your next physical attack deals an additional 100% of your Ability Power in damage. This effect has a 2 second cooldown.
This item is obviously very situational, and has quite a weird build up to it.  This item can be broken on a Master Yi built for AP or anything reliant on using standard attacks between skills such as Poppy or champions that need the Sheen anyways such as Ezreal.

Long Sword - 415g
+10 Attack Damage
This is such a versatile item and worth stacking and spamming because it literally builds into every early game to meta game DPS item.  Also sometimes a starting item.

Madred's Bloodrazors - 3800g
+30 Attack Damage +40% Attack Speed +25 Armor UNIQUE Passive: On hit, deals Magic Damage equal to 4% of the target's maximum Health.
Now some people seem to have some confusion over this item.  It is actually not that effective as a tank killer which is what this item was designed for, but the % of max health unique passive is the main source of damage for heroes that have crazy attack speed, but may not have the damage to back it up such as Teemo.  This is also a popular buy among junglers because you need the Madred's Razors anyways.

Madred's Razors - 1000g
+15 Damage +23 Armor UNIQUE Passive: 15% chance on attack to deal 500 damage to a minion.
If you're playing a jungler, this is a common item with few exceptions such as jungle Rammus.  Should only be used to turn it into Madred's Bloodrazors later.

Malady - 1405g
+25 Ability Power +50% Attack Speed UNIQUE Passive: Your physical attacks shred your target dealing 20 magic damage and lowering their magic resistance by 6. Magic resistance reduction stacks up to 4 times.
Wow, even after this item got a rework, this item is still horrible.  It literally only works for Teemo and that's only if he is going an AP route.

Mana Manipulator - 295g
UNIQUE Aura: Restores 7.2 Mana per 5 seconds to yourself and nearby friendly Champions.
Really only useful on it's own early game, but it does build into a Soul Shroud which is better later.  If you're laning with someone based on mana, your team will love you for it, and with good reason.  If your team mate started with a Meki Pendant or a similar item, when combined with this, it equals non-stop harassment.

Mana Potion - 40g
Click to Consume: Restores 100 Mana over 20 seconds.
The mana based version of the health potion, it simply adds mana.  Now this may be just me, but I really don't like the Mana Potion at all.  Not only does it cost more than the hp counterpart, it adds only 100 mana, basically like one more skill you can use in lane.  If you really think you'll need some of these, you should have started with a mana regen item to begin with.

Manamune - 2110g
+350 Mana +7 Mana Regen per 5 sec +20 Attack Damage UNIQUE Passive: 2% of your max mana is converted to attack damage. UNIQUE Passive: Each time you attack, you gain one maximum mana (3 second cooldown.) Each time you use an ability, you gain 4 maximum mana (3 second cooldown.) Bonus caps at 1000 mana.
This item is so good in my opinion.  Just because you play an AD hero doesn't mean you don't need mana, yet it's not wise to buy a solely mana regen item on an AD hero; it's simply not worth the slot.  In the Manamune's case, it not only gives you virtually limitless mana, it even adds damage and quite a bit over time.  It's also very easy to max out due to it's easy requirements.  Good for Corki and

Meki Pendant - 390g
+7 Mana regen per 5 sec
This is the starting item for mana based champions early game, because you can have your mana regen, but also 2 hp potions to boot coming straight out of base.  It is mostly used to make the Tear of the Goddess, which is a great item, and also builds into the Manamune and Archangel's staff.

Mercury's Treads - 1200g
+25 Magic Resist UNIQUE Passive: Enhanced Movement 2 Reduces the duration of stuns, slows, taunts, fears, snares, sleeps, and immobilizes by 35%.
One of the best boots, if not the best boots.  It is more expensive than the others, but it is also the only item that reduces de-buffs by 35% which is massive.  Laugh as you walk out of Galio, Amumu, and Nunu's ultimate.

Morello's Evil Tome - 2350g
+75 Ability Power +12 Mana Regeneration per 5 UNIQUE Passive: Reduces ability cooldowns by 20%.
This is a new item that I was originally not a fan of.  The mana regen is not useful because a champion needing this item will already have items that regenerate mana far faster than this item.  If you play AP and want to get a lot of CDR in one slot, this is your best option.

Nashor's Tooth - 2465g
+50% Attack Speed +55 Ability Power +10 Mana Regeneration per 5 UNIQUE Passive: Reduces ability cooldowns by 25%
Only useful for Teemo and Kayle, but if aquired early can be overpowered.  It has so much CDR and attack speed, but that's just it, nothing more (well the mana regen, but it's not noticeable).  It's an awkward item that only benefits very very few champions.

Needlessly Large Rod - 1600g
+80 Ability Power
If you can afford this, buy it.  It's essentially 2 blasting wands in one slot and builds into the two items that AP champions absolutely need.  If you can't afford to pick this up and need AP, you can just buy a Blasting Wand.

Negatron Cloak - 740g
+48 Magic Resistance
Epic when it comes to magic resist.  It's useful on it's own, and useful in the items it builds.  With magic resistance slim pickings, picking one of these up is always a good idea.  Even if you're unsure, remember it can always be turned into a Banshee Veil, which ise useful for everyone.

Ninja Tabi - 850g
+25 Armor +12% Dodge Chance UNIQUE Passive: Enhanced Movement 2
Core item for Jax mostly, but can be used on a few tanks such as Malphite and Rammus whose damage is increased by armor.  Even then, usually Mercury's Treads are viable than these.

Null-Magic Mantle - 400g
+24 Magic Resistance
Builds a lot of items, but only situational ones.  That being said, this is a situational item.  A common and better alternative for magic resist is the Negatron Cloak.

Oracle's Elixir - 400g
Click to Consume: Gives your Champion stealth detection until they die.
For some reason, this is an item that you should always carry against invisible heroes, yet no one wants to buy it because you lose it if you die.  That's simply ridiculous because I'd rather pay 400g rather than see the enemy Evelynn go godlike off my team mates.  Usually the tank gets this, because in team fights he has the least risk of dying, and teams tend to center around the tank in the "final push" anyways.  Note that this does not take up a slot if you activate the potion, so it doesn't drop upon death like Gem did in DotA.  That would be dumb.

Phage - 1315g
+225 Health +18 Attack Damage Passive: 25% chance on hit to reduce your target's Movement Speed by 30% for 2.5 seconds.
It's pretty good if you need a Frozen Mallet late game, but this item is pretty good on it's own.  A lot of people get this early for the hp and attack damage, both useful stats.  Also, you can sometimes get lucky with the slowing procs and get kills you would otherwise not have gotten.

Phantom Dancer - 2895g
+55% Attack Speed +30% Critical Strike +15% Movement Speed
This is a popular item among many DPS champions, but should really be built far less than it is..  In other words, it's an overrated item that costs a lot of gold, and doesn't actually offer any real stats that benefit most champions, albeit on certain full-crit builds traditionally used on Gangplank or Tryndamere.  The movement speed further improves Master Yi as well when combined with his ultimate, making him the fastest champion in the game, hands down.

Philosopher's Stone - 800g
+22.5 Health Regen per 5 sec +10 Mana Regen per 5 sec Passive: Gain an additional 5 Gold every 10 seconds.
Another gold generating item; however, this one really sucks.  It only builds into Shurelya's Reverie, which is hardly seen in games.  Some people use a strategy that includes buying 2 of these early game, filling out the rest of your slots, and proceeding to sell of the Philospher's Stones to open up the last 2 item slots.

Pickaxe - 975g
+25 Attack Damage
Flat attack damage that makes it an alright item, but usually it's better to stack some Long Swords, unless you are using this to build into another item.

Quicksilver Sash - 1440g
+56 Magic Resistance Active: Removes all debuffs from your character. 105 second cooldown.
This is not seen often, because most people fail to use it correctly.  If you time the active just right, this is essentially your get out jail free pass.  It only adds flat magic resist; however, so the Banshee Veil is often used in place of this.  Note that this is significantly cheaper, so if you find yourself in a pinch, just buy this item.

Rabadon's Deathcap - 3600g
+155 Ability Power UNIQUE Passive: Increases Ability Power by 30%
It adds a huge amount of AP.  It's unique passive further increases your AP.  This equates to this single item giving you the most AP possible on a single item in the game, making it essential for most mages.

Randuin's Omen - 2925g
+300 Health +80 Armor +25 Health Regen per 5 sec. UNIQUE Passive: 5% Cooldown Reduction and 20% chance on being hit to slow the attacker's movement and attack speeds by 35% for 3 seconds. UNIQUE Active: Slows movement speeds and attack speeds of surrounding units by 35% for 2 seconds + 0.5 seconds for each 100 Armor and Magic Resist. 60 second cooldown.
This item is really a great item due to it's versatility.  It synchronizes perfectly with the skills of some champions, and the active can be used both offensively and defensively.  For those of you that need an example, think Malphite ultimate knock up, with Randuin activation when they come down.

Recurve Bow - 1050g
+40% Attack Speed
The flat attack speed item, this has become significantly less popular with the changing of Last Whisper; however, it builds into Starks Fervor, and Madred's Bloodrazor's, making this not completely useless.  Attack speed is an easily obtainable stat in game, so there are many alternatives that get
the job done better than this.

Regrowth Pendant - 435g
+15 Health Regen per 5 sec
This item can be really annoying to others when you use it as a starting item versus champions that need early game harassment.  It's also worth stacking, as 3 of these will make your Warmog's Armor, and your Force of Nature.  I personally favor this as a starting item over the Doran's Shield.

Rejuvenation Bead - 250g
+8 Health Regen per 5 sec
Useless, only buy it if you need to make something with it, and even then make it fast because this
item sitting in your item slot is simply a wasted slot.

Rod of Ages - 3035g
+450 Health +525 Mana +60 Ability Power Passive: Your Champion gains 18 Health, 20 Mana, and 2 Ability Power every 1 min. Bonuses cap at +180 Health, +200 Mana, and +20 Ability Power.
This item gains stats over time, so it's best if you get this item early.  This is very viable due to the early game benfits of making a Catalyst the Protector.  It adds a fair amount of everything an AP
champion needs, and can be used to beef up AP tanks too such as Singed.

Ruby Crystal - 475g
+180 Health
You will probably be buying at least one of these regardless of your champion, because all champions benefit from hp, and this builds into so many useful items.  This can occasionally be a starting item if your champion has a regeneration skill to begin with.