I have my sewing kit in a soft zippered & pocketed fishing tackle box.  I have plastic boxes of assorted sizes inside (also purchased in the fishing supplies) to keep the odds and ends in.  You could use any bag or container that is portable and organized.  Different thickness and color threads will come in handy at mending time.  Clear nylon thread will always come in handy.  Safety pins have many uses, even the larger diaper pins.  The larger safety pins are great for threading elastic through a skirt or pants top.  Crochet hooks can be useful even if you don't crochet.  Use one to pull the snag back through your sweater.  You might also add a small non-colored beeswax candle for waxing thread to keep it from snagging and breaking.  Save old zippers, buttons, hooks & eyes from old clothes before discarding or making rags of them.  Use your old cotton clothing for bandages for your first aid kit and rags for household use.  Scraps of old jeans make great sew-on patches.  Make new things from old clothing.  That dress that grew too short might make a nice skirt by cutting it off just below the armholes and adding a waste band or running elastic through the top.  That old shirt might make a good apron.  That ugly thing Aunt Jessie gave you years ago that has been taking up space in the back of the closet might make good pillow cases or kitchen towels.  Be thrifty and wise.