The runes I chose to use are:
Greater Mark of Magic Penetration
Greater Seal of Armor
Greater Glyph of Scaling Ability Power
Greater Quintessence of Ability Power

I chose Greater Mark of Magic Penetration because it gives quite a bit of armor pen, which gives you a considerable damage boost, as well as makes champs like Cho'Gath less of a pain!

I chose Greater Seal of Armor because it gives me a more survivable champ. An alternative could be Greater Seal of Replenishment but I personally never see any mana problems with Fizz, he is very efficient if played correctly.

For the glyphs I believe that Greater Glyph of Scaling Ability Power is best because it adds to your damage output.

The Quintessence's I go for all out damage, because if you kill an enemy within a second who needs to stack survivable things? I believe that the best choice is Greater Quintessence of Ability Power

The best skill sequence Ive noticed so far for max damage is:
first start with Chum the Waters which will take your target down a considerable amount
then Seastone Triden and then quickly use Playful/Trickster to quickly move to my targets location, as well as do massive amounts of damage with the two abilities combined. Then to finish them off a throw up an Ignite if needed, and use Urchin Strike to get the final devastating blow.

Ignite Teleport

I use these two because they help me get that last bit of damage in, or stay in the lane longer. Other options may be flash and serge, it really depends on your play style.

Pros:
Massive damage
Easy to use
Fun to play
Versatile
Good minion farm
Hard to kill

Cons:
easily and often focused
weak beginning of game