pros

insane amount off ap for an off/tank or ap bruiser.

high amount off mana boosts singed's passive, seraph's embrace and muramana greatly.

seraph's embrace's unique active enables you to bait extra long
(because it gives you a shield based on 1/4 off your current mana) (that is a 400-900hp shield)

muramana's unique passive works on your FLING (E) and basic attacks , giving you a better damage burst and sustain.
(the boosted damage costs 3% off your current mana and deals 2ce that amount off damage
wich starts from 260 ap damage and goes down 3-4% on every hit from that point)




cons

you are less tanky then other builds and without the extra mr items you are quite squishy for ap damage without putting your ulti on

having a TEAR in early game makes you weaker because you could have another item wich gives you higher stats.
But dont worry because since your singed you can charge a TEAR to its maximum within 20 minutes and changing that into a SERAPH'S EMBRACE is all worth it because it is cheap and it is one of the most powerfull items in the game.

some tips for teamfights

before a teamfight has started look at the enemy champions and at there items.
now what are you going to do or who are you going to focus?

first of all make sure too use your ulti just before entering the teamfight because it lasts 25 seconds and bye that time the teamfight is already over so make use off that extra
ap/armor/mr and movement speed bonus so that you wont need that regen.

after that you are going straight to the back (while poisoning everyone)and throw the carry towards your team so that you or one off the other teamates who are smart enough to focus the carry can kill her/him

depending on the champions that are on your team and on the enemy's team
you can decide to slow a champion who has weak mobility and needs to be up close and in that way prevent it from getting near your carry or any other damage dealer.

those are champions like sion/gangplank/renekton/rengar etc

when laning as singed you are fairly weak early game.
it is often best not to play aggressivly before you are lvl 6 or bye a given oppertunity

when you encounter another melee champion it can sometimes be wise to unlock your "E" first
and to throw him inside a group of minions and then to attack him with basic attacks , he will be forced to run out off the group and take the few extra hits.

try not to use your poison for farming because you will end up pushing your lane to much making it unable for your jungler to gank and enables the enemy jungler to come in for an easy gank
especially early game/when you dont have ulti.

if an enemy jungler appears and you know that you are tanky/healthy enough to stay alive for a long time
then switch your ulti on and start poisoning away, try to make use off the double bush at top and juke your way between them a few times back and forth (this is done bye just touching the very tip off that bush and to walk back at the very moment your enemy's want to enter that bush)
they will soon find out that they can not follow you any longer so make sure you can throw/ignite them before that happens.

also do not forget that even though you are a tank that you are not unbeatable making that mistake can cost you your lane and game.

when you are at low hp run away to regain some hp from your ulti try not to run to far away from your teamates because they could still use your slow to escape or kite an enemy.
your poison might be able too help out to or you could also use singed's throwback skill for when the remaining enemy is in a tight battle with your remaining ally(s).