Echoing the above about making the lettering clearer. If hand-lettering isn't something you're looking to perfect, there are a lot of quality free comic fonts available online. I personally use a font because I know I can't maintain a consistent lettering style. Also, plan the panels out so that the dialogue and artwork are not competing for space.
If you're looking to up your quality overall, I'd say put a lot more care into the presentation. I see your panel borders are often uneven and have lines poking off the ends. You can use the rectangle tool in Photoshop to get an even shape, or just draw a straight line with the brush tool by holding down the shift key. In general, you should make sure that your gutters are spaced out evenly, and that art isn't popping out of the panels unless there's an intended reason.