It could enhance his senses. Maybe the suit has sensors that can detect things that his normal senses can't. For instance, it could detect hidden traps or enemies that are invisible to the naked eye. This would make him much more vigilant and better able to protect the city.
One idea could be a suit that has the ability to change its color and texture to blend into different environments like a chameleon. This would give Spider - Man an added advantage during stealth missions.
Spider - Man could develop a new sense of confidence, but also arrogance. The symbiote suit makes him stronger and more powerful, so he might start to think he can handle any situation alone. This could lead to him pushing away his friends and allies, like Mary Jane or Harry Osborn, until he realizes the error of his ways.
A good Spider - Man black suit fanfiction often has a strong understanding of the character. The black suit changes Peter Parker in many ways, and if the writer can capture his internal struggle, like the balance between power and responsibility, it's great. For example, if they show how the suit's influence might make him a bit more aggressive while he tries to hold onto his core values.
One popular storyline is the struggle of Spider - Man against the symbiote's influence. In these fanfictions, he often has to fight his darker impulses while wearing the black suit. Another is his relationship with other characters like Mary Jane or Gwen Stacy while in the black suit, which can add new layers of drama.
One popular plotline is the struggle with the symbiote's influence. In many fanfictions, Spider - Man has to constantly fight the darker urges the black suit brings. For example, he might be more aggressive in his fights against villains, almost crossing the line into excessive violence. Another plotline could involve the suit having its own consciousness and trying to take over Spider - Man completely. This can lead to some really intense internal battles within Peter Parker as he tries to maintain his identity and moral compass while dealing with this powerful and malevolent force that has attached itself to him.
Perhaps Spider - Man stumbles upon a hidden cache of vibranium. It could be in an old, forgotten laboratory or a secret vault. He then takes the vibranium and with his own knowledge of suit - making and some help from his friends in the science community, he constructs the vibranium suit.
In some fanfiction, the Venom suit could give Spider - Man new abilities that he has to learn to use. Maybe he discovers he can create shadowy tendrils that can grab objects from a distance or form a protective shield. This could lead to him having to train in secret to master these powers without his friends finding out.