I use this build often and i have yet the lose with singed while using this build. The idea is that singed is loaded with with health early and then given AP to increase the damage your poison trail leaves. With this build you can jump into team fights as the initiator and still be able to get out of the fight any time alive either with flash or running out with poison trail on added with rylai's crystal scepter. the poison trail will slow your enemies enough for you to make a quick getaway also while you have your ulti and force of nature on you gain and insane health regen either to getaway and survive turret dives or heal while pushing turrets or being decoy for your team. To me singed can use flash and or ghost to help but the most useful spell I found to be early game is exhaust because it give your lane an easy first blood. For example you and your teammate jump into the bushes and find an enemy you instantly fling him back since your fling cooldown is pretty short he should be quite weakened and start running that instant you use exhaust to trap him giving you time to fling him back once more if need more speed then flash and ghost would be your option to use to catch and fling the enemy back to gain first blood with your lane partner. Early game you will often run out of mana fast because of your poison trail well to fix that either get your ally to help u gain the blue buff or just do it yourself if your confident enough. Late game you can keep singed's poison trail on for as long as you want with out worrying about mana because of the boost given to u by Rod of ages and Frozen heart.

I hope this helps new singed users better understand and master singed thank you for reading this build and good luck in your battles.