cabled vest/cowl - *Inspiration* this one is knit but you could easily crochet this so pull out your favorite scarf pattern and get to crocheting. You may need to adjust the width of the scarf. Once your scarf is long enough, wrap it around yourse.
Back exercises! Your back is a big part of your core and can be weak if you sit all day at school/work. Strengthen those stabilizing muscles and you will notice you maintain better posture throughout the day and feel stronger through your whole core.