tattoo needle depth

Hey everyone, Still pretty new to this so excuse my noobness :( I can't seem to get a clean solid single pass line, or even close to it. I usually do the whole tattoo, wipe, then have to sculpt in the lines over top of the first pass to get a really solid stable line. It feels like sometimes...

My friend asked me to do a tattoo for him - I am at the stage where I would only ever do a friend/ someone i know and who understands 100% I am learning and that I think I oculd do the best job I can on it - I am years away from being at the stage where I would ever do anything on a stranger...