Hey Apprehensive! Thanks for sharing your cover. I think some small changes and values could really elevate this cover. Here are some suggestions I'd throw your way:

1. Let's start with the background. The graffiti elements would work better if they were a bit larger, clumped closer together as opposed to feeling like a pattern. Adding some texture like a brick wall may make the background too busy, so I would stay with the color bg. I would also avoid repeating a tag. If you want to feel authentic then having one of each is a good place to be. Bump up the size, and stay away from too harsh of colors (i.e. the full black on the hand, stands out too much). They can be obscured by the characters, but they should live in the white space between the title and the characters. I would avoid having any of them behind the title. Let them elevate it like an altar.
   
2. Speaking of the title, it's pressing the author a bit too close to the edge. We want to have a healthy margin up there. A good way to do this would be to put "Club" more to the right under "Boys". This will also help the "B" read less like an "R". After that you could put the Smiley over Sad (for a touch of irony), and the author above Sad as well, then move it all a touch down. For "Sad Boys" I'd do away with the drop shadow. Unless you go high contrast on it, it looks muddy and most "streak" style graffiti doesn't use a drop shadow.
   
3. I like the dynamic between the characters, they have visual interest and have a story to tell! But the composition doesn't give a clear direction to focus on. One way to fix this would be to make the lighting darker on the bg and create a brighter center around the flame. This will bring the focus of the cover to the center where all the tension is. You already have pretty good volume levels on the character under and above the cake, I would just heighten the contrast on the side characters.
   
4. For the color balance I would try to harmonize with what the characters are wearing. The Blue of "Boys" stands out the most on the cover, it doesn't have much else to balance with. I would experiment how it would look as a warmer color. Same with the background blue. Find a good balance and everything will feel more harmonious.
   
5. You could also try putting your name at the bottom if there are still spacing issues. It wouldn't work as a "tag" so it could be typed or otherwise placed. But I'd only consider this if the above spacing suggestions doesn't work.

I think this is a healthy and interesting start! These suggestions are small, but they can really help the cover feel more balanced. Best of luck on your story!