How can I improve my binding process to get a better result?
You could punch holes through the leaves, and sew, using an asian-style bind, or use overcast sewing before binding. You will need an awl, or drill/drill press to punch holes through the paper before sewing, though, and of course, you're losing more of the edge of the paper than using folded signatures and the book won't open flat.  But you will have a proper sewn binding that doesn't rely on glue to keep the pages in, and will be more archival in quality.