This singed build is my favorite. The items you use are manly used for versing people that don't really focus too much on AP, but either way you still do good against AP enemies.

I chose Greater Mark of Insight, because he is a AP character and magic pen is a good fit for him.

I chose Greater Seal of Resilience, because armor makes it so he can take more damage and that helps a lot with singed.

I chose Greater Glyph of Shielding, because again he is a mage and magic resist can help versing other AP characters or enemies that use AP attacks.

I chose Greater Quint of Swiftness, because swiftness helps singed escape, get around easier, and chase enemies trying to run away from him.

Offense:0
I chose no offense runes, because he needs to focus more on utility and defense in my opinion.

Defense:9
I chose 9 defense, because it helps him take more damage while fighting against 1 or more enemies.

Utility:21
I chose 21 Utility, because singed is a mage and utility manly focuses on AP.

The Items i chose help with mana regen, health regen, defense, ablity power, and other things which helps take down more enemies and stay in game longer.

I usually use clarity and heal, but if i put that people would probably call me a noob, so i am going to go with flash and ignite for my summoner spells. I chose flash because it helps singed get away quicker or get to a enemy who is running away faster. I chose ignite, because it helps deal damage to players who are at low health.

Hope you like this singed build and might want to use it!! ^_^ if you have any suggestions on improving it please comment letting me know. :)