If you are looking to improve your Gmail productivity, the first place to start is with keyboard shortcuts. Never using your mouse or trackpad to navigate Gmail is the biggest time saver you can do.
First, you need to enable keyboard shortcuts in the Gmail SETTINGS menu.
Master these top commands:
c - compose new mail j - go to previous mail k - go to next mail e - archive (goes to All Mail) r - reply gi - go to inbox ga - go to all mail gd - go to drafts l - label gl - go to label
Full list of shortcuts here