Singed mainly a tanky support champion, I buy will of the ancients for spell vamp, thornmail for reflecting minions attack, Ryalai's for slowing down enemy backward and increasing singed health. You can get pretty high health, ap and armor in the later game. This build can easily be very tanky in game, a high armor can make sure singed can carry vs some high damage champion, e.g. tryn, master yi.

I picked Greater Mark of Insight for magic penetration, Greater Seal of Resilience for armor, Greater Glyph of Intellect for increasing mana and Greater Quintessence of Potency for ap. Armor
and mana runes can make you carry a long time in side lanes.

Singed descended from a long line of Zaun's revered chemists. Even in his youth, his talent for concocting potions far outstripped that of his peers, and he quickly distinguished himself from his less extraordinary chemist compatriots. It came as no surprise to anyone when he was selected for apprenticeship by the infamous Warwick, master apothecary on a lucrative retainer with the Noxian military during their campaign against Ionia. Within Warwick's laboratories, Singed toiled without end, rapidly absorbing every detail of his predecessor's deadly craft. Singed had little concern for the death and destruction that was the fruit of his labors. By the time the curse of lycanthropy descended to claim his master, Singed was poised and eager to make the transition from workhorse to innovator; he was ready to share his genius by bringing a new brand of suffering to the Ionian front. His zeal for progress was unquenchable, and when suitable test subjects proved to be in short supply, the eager chemist was often thought to turn his volatile mixtures on his own flesh.

When the uneasy peace created by the League of Legends settled on the world, Singed journeyed to the one place where he was still able to showcase his beloved craft: the Institute of War. By this time he was barely even a man, his body both ruined and sustained by his ingenious craft. A thousand burns - accidents of shadow and flame - mar his ravaged form, and exposure to such harsh conditions has deadened his nerves, hardened his body, and strengthened his physique, transforming him into a veritable juggernaut. This, combined with a formidable arsenal of deadly concoctions, makes Singed a force to be reckoned with on the Fields of Justice.

''My deadliest dose shall bear my patron's name!'' - Singed, having just christened the Insanity Potion