Before I get into the actual play style, I would like to add the possibility of adding an elisia's miracle to the build for the passive effect.

The play style for singed especially needs to be very controlled and situational. You need to use your speed to your advantage. Don't run around in team fights, run through them and let the poison take it's toll, then come back around after disengaging. Throw works great for singling out a single person on the enemy team to be targeted. Use the adhesive for area control and just as a regular slow to stop their escape.

In short, know you're limits and use your speed to your advantage.