I've written a lot about combat in various topics on this board. So look around and find my posts as well as useful advice from other people. There is also a video topic that was posted which is a valuable resource.
I am quite sleepy, so I may be incoherent:
Focus on not getting hit. Focus on mobility. Use your offensive attacks primarily to stay alive, not to do damage.
Lose the idea that your goal is to hurt or damage foes. Instead, replace it with the idea that your goal is control foes and stop them from being effective in any way.
Remember, Spider-Man can splatter their skulls with a single punch. He can even break their bones by simply flexing when they punch him.
Spider-Man's goal is not to hurt them, but to slow them down, stop them, control them, hinder them, stifle them, and make their efforts futile.
Make that your goal. Hit one enemy so that he flinches, then hit another and hop over him. Dodge. Yank another into the air for a combo. Dodge. Webstrike the distant gunner so he can't shoot. Launch him and web him when he hits the ground. Dodge under the whip enemy so he can't whip. Perfect dodge the brute so he gets webbing in his eyes. Dodge the rocket. Web the rocket man to the wall. Dodge. Jump. Dodge. Jump. Dodge. Jump. Circle. X. Dodge to the wall and Square for a flying punch, knocking foes to the ground. Focus on who ever is trying to attack you and leave the rest for later.
Practice, practice, practice. And realize that I got the game in early January and am still finding ways to improve. So be patient with yourself.
TAZ "It's not who I am underneath, but what I do that defines me." -Xtreme65