9 Glyphs: -5.89% Cooldown
9 Seals: +11 Mana Regen/5 at level 18
9 Marks: +8.5 Magic Penetration
1 Quintessence: -2.39% Cooldown at level 18
2 Quintessences: +3.78 Magic Penetration

Usefull Combination to keep you at lane with the Mana Regen.
Cooldowns gives you the bonus to have Ultimate very often. [48 sec CD at lvl 18]
Magic Pen allows you to focus tanks if needed [Don't forget your Null Zone]

I like starting with boots and 3 health potions. That's because the extra speed is usefull to run away if you see your enemy initiating or even using skills to eliminate your creeps. The health potions will keep you at lane until 6 lvl when i go back to base for first time with enough gold for Tear of the Goddess. [Note: After buying Tear of the Goddess spam spells on creeps to max the passive as fast as possible] My next priority is a Blasting Wand to increase a bit my damage output and then to upgrade boots to Sorcerer's. I prefer to buy Sorcerer's shoes first than archangel's staff because the amount of mana from the unique passive is still low. And now it's time to farm for rabadon's... If the game is going well and you pick up kills or you farm really fast buy Needlessly Large Rod first and then Blasting Wand. If you are getting pushed and you see it's gonna take ages to farm 1.6k gold buy the Wand first. Then buying the Void Staff is just perfect. You have already a huge amount of AP and the +40% magic penetration in addition to your null zone will eliminate any tank in no time. Giant's Belt next is to increase your stability in team fights. Then grab another Blasting Wand and an Amplifying Tome and upgrade then to Rylai's Crystal Scepter. That's a really good item and let me explain why. You're getting chased and you have like 300 life, if there is 1 guy after you [And your ulti is on cooldown] just use malefic visions on him and his speed will decrease enough for you to be safe. If there are more guys chasing you use null zone right behind you and all of them are going to get their speed decreased. And finally a lich bane will make your enemies rage for sure. If 1v1 you make your combo and lets say enemy doesn't die... Your next simple hit will deal a huge amount of damage that will finish him for sure. Also the bonus speed is good to chase or escape when needed...

Personally i use about 3-4 combinations depending on the enemy and how he's playing.

If he's a slow player [reacts really slow] use Silence first, then Malefic Visions, Null Zone and your Ultimate, Nether Grasp. [Note: While you cast your ultimate you can use Ignite on him so if he had any chance to survive now it's gone]

If he's not a slow player and he avoids your Silence easily then use Malefic Visions first, then Null Zone right behind him [most likely he's gonna run back] and then Nether Grasp and Ignite. If he survives place your Silence on his way back or flash and use Malefic Visions again.

Another smart way to pick up a kill at mid is to wait until enemy's last creep is dead and Malefic jumps on him, use Flash to surprise him, Null Zone, Nether Grasp and Ignite and then cast Malefic again.

Flash: Easy escapes over walls, easy gangs flashing over bushes behind your enemies and generally a good way to surprise attack someone.

Ignite: An extra spell in your combo is always good, nice way to kill champions with high Lifesteal [Nocturne/Nasus] or Spell Vamp [Vladimir/Fiddlesticks]

If your team is pushing a lane, malzahar is the guy that will make enemies stay back. Spam Q and W in front of them and they won't dare to initiate. Also if any of them comes closer use E on him and he will run back probably.

In team fights focus their carry or their support. Use Call of the Void and Null Zone every time they are available. Supports like Soraka , Sona, Taric, Karma, Janna MUST be focused by you so they wont heal their allies or use any CC on your allies.