I trim every time and clean every time. I have picked out a lot of defective brass by checking it when trimming. Some factory defects (I size and trim new brass) some defects from firing. Being new to reloading, you should stay away from neck sizing. I have been doing gun work for almost 40 years and reloading has caused more problems than it ever solved. Read your manuals and go slow until you get a basic understanding of reloading. Be leery of reloading "Advice".