This is a Nunu guild I am currently working on. After the buff to his passive and consume Nunu's sustain in lane has increased 10 fold (not exactly 10 fold but it has increased a lot). With this sustain Nunu can easily bully their lane counter part and out farm them.

9 Offence - I get the 10% magic pen because this plus the void staff gives 50% magic pen!!

9 Defense - I take the armor buff but the main thing here is the 30 hp at lv 1. It helps you in the laning phase

12 utility - I get the mana regen to help with some mana issues then the move speed to rape, and the extra duration on my blue buff wich will devastate the enemy laner, and finally the 3% spell vamp for extra hp when using consume.

Magic Pen Reds - Gives a decent amount of magic penetration early game, enough to make your iceball hurt.

Armor Seals - Since most ap mids are ranged you will need these over mana re gen, plus the buff to your passive makes your mana usage less.

Flat MR Glyphs - This helps you alot agianst champs that will constantly harass you with their spells Ex: Ryze. The reason I go Flat MR instead of MR per lv is because that you need to all the buffs you can get during the laning phase so you can bully your lane counter part.

Flat AP quints - 3 of these give you 15ap and with the doran ring you start with you get 30+ ap at LEVEL 1 PLUS your ice ball ap ratio is 1.0

What you do during the laning phase is shut down the enemy laner. Ice ball ever time they get in range, if you get low on mana ice ball every time you have your passive up. FARM FARM FARM no use of shutting down the enemy if you shut down your self, last hit as much as possible. TIP - if you need to put an extra lv in consume in the early lvs, PUT ONE.