Luden's Tempest

You NEED to buy this if you want to one-shot your opponents. This Mythic Passive is essencial.

Rabadon's Deathcap

C'mon, this is too much damage. My favorite item.

Lost Chapter

Lost Chapter is essencial. Your mana problems will be meaningfully reduced after this acquisition.

Mejai's Soulstealer

This is not a final build item. Really good to stay strong.

Blighting Jewel

Better then Mejai's, only because can be used in the final build as you're going to buy Void Staff. Magic penetration is really good to make you stronger.

Zhonya's Hourglass

This is essecial only if you aren't very experienced or if your opponents can combo and explode/kill you really fast. Nice tech option in this second case.

Morellonomicon

This is essencial if you need Grivous Wounds (to stop the healing of your opponent). I like to buy Oblivion Orb early game in some of this cases and later sell it to buy other complete item in the late game.

Banshee's Veil

This is essecial only if you aren't very experienced AND your opponents can easily stun or bind (Exemples: Morgana, Veigar, Zoe).

Void Staff

Magic Penetration is always good in this build. Really good to One-Shot your opponets.

Cosmic Drive

Nice option to make your Q more effective, because you can chase better with the extra Movement Speed and Ability Haste.

Demonic Embrace

Good option agaisnt tank-ish opponents. The extra health and it's passive effect can be good for a little more sustain.

Liandry's Anguish

You will deal significantly less damage, but your R will be coming back faster, so...
...maybe this is a nice trade (only if you're a SUP).

Archangel's Staff

Mana won't be a problem with this. I like this as a situational item, if you are a heavy poke SUP or a aggressive fed MID/APC. Tear of Goddess can be useful to buy with your excess early money to make your Q more effective, because you can use more (and make your E stronger in the same way and to farm easily).

Chemtech Putrifier

This is basically a Morellonomicon with Ability Haste. If you want to make the Full Ability Haste option, buy this, but remember: This options deal less damage.

About boots

You have basically 4 options. In order of significance, from the best to the worst:

• Magic penetration: Everybody likes to deal tons of damage. This is the strager and funnier option.
• Magic Resistence: If your opponent is AP, this is a great item of defese. Plus, the tenacity can be really useful.
• Ability Haste: This is a good option if you're playing as SUP. In others roles, you should focus on defense or damage.
• Movement Speed: Great option to be free to gank at level 6 or more. This is a good option if you fell behind early, but it isn't a final build option (in my opinion).

BAN

Basically, ban ranged and/or poke-ish champions that you fear. They can bully you and you will not farm well, and then will be snowballed.

FARMING/LANING FASE

Move around the minions wave to prevent poke damage. You should try to farm without skills in the early early game (before first base/buying The Lost Chapter).
Use W to farm siege minions and to farm a little bit better.
Use E to push the lane and/or farm multiple minons at the same time.
DO NOT USE YOUR Q TO FARM, unless it's a siege minion AND you are confortable with mana.
Before buying The Lost Chapter, you should try to use Q only to eventually make your opponent less confortable. After buying the item, you should try to use Q more to bully him and consequently farm better/more comfortably.

Farming is essencial to make you stronger. Initially you are weaker than most of the midlaners, but if you are even or just a little bit behind in the midgame, you probably can solo everyone.

MID GAME

If behind in the early game:

• After level 6, you should try to gank someone to gain more gold with kills. You know your R is insanely good.
  

  Maybe, just maybe, you should buy Mobility Boots to increase your chances to gank better and lose less farm in the process.

• Don't be afraid of asking help from your jungler. Do not push your lane, because
  

  low lane + R(or even only your Q, depending on the opponent champ) + jungle gank = certain kill

If you are fed early game:

Execute order 66. Just kidding, but you should use your advantage to:

• Make objectives. No one can make Dragons nor Rift Herald while you have your R.
  

  R + Your Jungler = steal any objective

  
  

• Help other lanes. A gank with your R will most of the time be a kill.
  

  Be careful against opponents more fed then you or toplaners too tank-ish and a little bit fed.

MANA CONTROL

This section is only to remind you to avoid using the skills if you're running out of mana. For real, you should learn the cost of your skills and ratio your mana.

COMBOS

You are a Malphite! Just use your R to start team fights.

Complete combo: R + E + Q + hit + W

BAN

I don't have right now a SUP to suggest to ban, but I can suggest to ban type of SUP: Ban what you fear most the is ranged or can stun/bind.
If you want to ban a ADC, I suggest to ban the ones with big ranges (Examples: Ashe, Caitly), but if you want to ban another champ, nobody will judge.

WARDS

As a good SUP, you should learn to ward wisely. Vision is essential to your team and you can even (maybe) surprise someone in the jungle or a bush with your R.This is a image I found googling and made some addictions.

MANA CONTROL

I know you like to poke, but sometimes you need to be patient and poke less to make more profit level 6 or more. Try to not focus the opponent SUP (for all rules there are exception).
You should try to rhythm your Qs with the cooldown of your Support item.

Some early game tips and

MID GAME

Stay with your ADC. You want him to be fed, not you. With good vision you can be helping your jungler with objectives.
Save your R for stealing objectives (with your jungler) and targeting 2 or more opponets (and/or the ADC) at botlane. Be careful to not (always) kill the opponets. Remember: You want your ADC to get fed, not necessarily you.

COMBOS

You are a Malphite! Just use your R to start team fights. Your Q can be a useful option to start a 2vs2 botlane.

Complete combo: R + E + Q + hit + W

BAN

Ban Ashe, Caitlyn or Kog Maw. They have a really big range that can bully you. Most ADCs can bully you if they play well, but these three are impossible.

FARMING/LANING FASE

Move around the minions wave to prevent poke damage. You should try to farm without skills in the early early game (before first base/buying The Lost Chapter).
Use W to farm siege minions and to farm a little bit better.
Use E to push the lane and/or farm multiple minons at the same time.
DO NOT USE YOUR Q TO FARM, unless it's a siege minion AND you are confortable with mana.
Before buying The Lost Chapter, you should try to use Q only to eventually make your opponent less confortable. After buying the item, you should try to use Q more to bully him and consequently farm better/more comfortably.

Sometimes you will need to farm below your tower, only experience can make this easy. Tip: positioning around the minions + E can be useful.
You can be a little bit greedier if your SUP have a healing skill.

Farming is essencial to make you stronger. Initially you are weaker than most of the midlaners, but if you are even or just a little bit behind in the midgame, you probably can solo everyone.

MID GAME

If behind in the early game:

• You should learn to farm below your tower.

• Don't be afraid of asking help from your jungler. Do not push your lane, because
  

  low lane + R(or even only your Q, depending on the opponents champs) + jungle gank = certain kill

If you are fed early game:

Execute order 66. Just kidding, but you should use your advantage to:

• Make objectives. No one can make Dragons while you have your R.
  

  R + Your Jungler = steal any objective

  
  

• Oppress your botlaner's opponent. Destroy towerS with your W. Muahahaha!!

MANA CONTROL

This section is only to remind you to avoid using the skills if you're running out of mana. For real, you should learn the cost of your skills and ratio your mana.

COMBOS

You are a Malphite! Just use your R to start team fights. Your Q can be a useful option to start a 2vs2 botlane or to poke them to death.
I suggest to wait your SUP to do something before using R, if it is an aggressive SUP. Other option is to use R below your tower or, if your SUP or jungler is well positioned, if the enemy's ADC and SUP get too close to one another.

Complete combo: R + E + Q + hit + W