Nice attempt. Here's my commentary, hope I can help:
1) Why did you resize down to 825px height? Use 1100px or 1200px for best results.
2) You need to spend some more time giving enough space around the text. The text should not be close to touching the edges of panels nor bubbles at all. The very first bubble, the HENGE! bubble, the GENTLE! bubble, and the very last bubble are all examples of this. Stay away from those edges! Usually this is done by decreasing the font size.
3) In many other bubbles, the text is not centered. You did not spend enough time positioning the text. They are for the most part way too high. Use the arrow keys on your keyboard to nudge the text into place. Don't stop till it looks perfect to you. Read more HQ Edited Mangas to see how the text in those releases are centered.
4) Pretty nice job on the SFX - just one thing: they need a white stroke around them. To do this, right click on the layer that contains the SFX text, select Blending Options, click on Stroke (on the left), and set the stroke to white, 1-2px in width, and outside.