Sewing requires concentration and hand-eye coordination, which keep the mind healthy and active.  Plus you get a sense of accomplishment that comes from creating something handmade, even a simple garment. 
      Here is a Simplicity Crafts Sewing Pattern  #8314,  Size 18" Tall Doll Clothes,  Fun Wardrobe, featuring a Dress, Romper, Top, and Pants.  Find fabric that catches your eye and add some personal touches.  Add details that make it so beautiful for a lovely result.  My best recommendation is do not use thick fabric.  Vintage 2017.  This pattern was never cut, never used.  Happy sewing!  Thank you for looking.
Some 18" dolls:  American Girl,  My Life,  Our Generation,  New Adventures,  Journey Girls