Here's a tip for Singed. Don't build with his passive in mind. It's pretty crap. RoA maybe, but it's generally better to have two Doran's Rings or two Dark Seals for early laning instead of a Tear. A general idea is, if your team is pretty AP deficient, rush Rylai's and Liandry's, that's generally enough to do damage. RoA if you think you can squeeze it in, too. After that, just go tanky, preferably with a Dead Man's Plate in there.
As for GAMEPLAY tips... Never engage your lane opponent unless they're super-weak early game. You're too mana-hungry early on. Always poison the enemy minions in such a way that the poison lingers over your minions to zone the enemy out. For teamfights, you either wanna do your best to keep the CC-heavy enemies away from your team or rush through the team to fling their carries out of position. Try to provoke people into a chase, they'll probably do it at least somewhat before giving up, but by then you should be able to finish them off with a gooflip. Oh, yeah. Practice the gooflips. Two ways of really doing it... If you're chasing, put the glue in front of you, preferably so they have to go through it. If you've caught up, fling 'em back in. The other way is to set it up behind you if you're getting aggressed on and then just lob 'em in.