I am a bronze singed with 50k mastery. I have played singed constantly and I have an idea on how to use him. To start you want to avoid using poison at the start due to mana issues. If the enemy approaches you do you best to run away with poison on. After you have enough money you can go back and get a hextech revolver for protobelt and/or a corrupt potion to help pressure hard top laners such as darius. When you are 6 you can take fights as long as you have they mana. To engage run up and put adhesive behind and then try and fling them into it. If you do it roots them giving you an advantage. If you don't its ok just run and try to kite. If they run away walk with them and also use auto attacks for extra damage. This will proc conqueror and help you heal more. If you used aery then thats ok just try to kite as best as you can. Against ranged is a bit difficult. Flash fling really helps surprise them.

You made it to the mid game. You want to help your team with objectives and if possible split push while your team keeps them busy. If someone does come you can go inside a bush and put adhesive down. When they come fling them and run away. This will almost guarantee escape as long as there isn't others to stop you. Late game you want to be with you team and be the one to engage. Flip the squishy targets in the back and run around trying to dodge what you can. The rylai and liandrys will help you team be able to engage. If you go down its fine. They are gonna most likely focus you because you are in their faces. Going down early without getting your poison on their backline is really detrimental and can cost the team fight so if you think you can get to the backline without getting bursted down then go on ahead.

If you lost the laning phase then it going to be a bit trickier to catch up and be of use to your team. As long as you didn't feed a crazy amount of kills you should be fine just farm up in the mid game and try to help your team as best you can by split pushing. Since you aren't exactly helpful in a team fight being behind try and avoid them as much as you can. Go to lanes that don't have anyone and get that cs. Once you have 2 items and you are level according to your top laner (one level behind is fine) then you can start to engage in the team fight toward the mid/late game. Surprise flash flip the carry in the back and run through their team. Use adhesive to prevent any escape and run to victory. Since your passive gives move speed off of both allied and enemy champions you will be extremely fast and might be able to escape. If they chase they will get poisoned to death.