Don't overuse trick stabs only go for them as a last ditch effort to live if you use them too much you are just gonna get countered. Also if you are practicing spy don't use the dead ringer It makes terrible spy habits.
Don't go for trickstabs. Be a spy - play stealthy, wait it out. Go for the correct picks. Blend in - pretend you're really a part of the other team. Know what the map is like. Understand and expect your enemy's movements,
And act upon them.
try to understand the team play style and and just try to be a pain in the butt for them. Keep them looking for you(risky) and If you can't kill them,distract for as long as possible to keep them away from the objective.
Or just try to pop heads with the Amby all day and be relatively useless like me