First , when I looked at this champion I thought how he can be viable, he is not a tank nor a caster. After some practice I knew that his great tanking abilities, movement speed, ability to put some chaos to the opponent team in teamfights , great farming abilities, make out from him such a great and character to play!

I don't really have a Runes build, because I don't have full rune pages. However, Hp or movement speed Quints, Armor and M res is viable for me.

Here we got 2 options, we may go full tankish, and develop Defense masteries, or if we want to have less problems with mana, and also have more movement speed, we may go with Utility tree.
Choice is yours.

I am starting with a dorian ring, mostly because of variety Most players start with Mana crystal and potions , which is good item for start too. However I like to start more "boosted"
Then I rush ROA, this item provides a lot of health as long with his passive, and ability power. Next are boots, with more movement speed than others we may use our <Q> posion trail more effectively. Rylai goes with nice ap, hp boost and also with Slow passive. <they can't catch us now , can they? >
Next 3 items are much like for balanced Opponent team. Of course if they got more mages u may go with Abyssal Scepter or other MR item. If their team is full of ad carries, go with thornmail.

I max Q at first, because of his farming abilities. E goes second because Singed lacks of damage. Heavy slow for catching and escaping is more needed Late game.
I take Ulti whenever I can.

Well for Singed I don't see much option here. Ghost is when I have to get out of big trouble, and for more effective chasing, so is flash.

PROS

Great movement speed
He shines in team fights,
Provides great support, and protection for his teammates

CONS

Lack of "hard cc"
Not as beefy as other tanks
Takes some time to get used to

Ah he is perfect farmer. Just let his Q go around the creeps, and watch how much u will earn. If your lane is empty, don't forget to call mia and just go Ahead (Even before your minions) and creep more and faster. If u are pushing tower with nobody on a guard do the same.

This is my first Guide. So please take into consideration that, as well as that English isn't my mother tongue, and my opinions may differ from yours.
Please comment rate, but don't flame.

My Guide isn't very FLASHY but for the time being I am not able to handle Coding to make it prettier.
Thank you for reading it.