I would consult the Canadian Food Guide, or the American Food Pyramid to ensure that you are well-nourished according to those standards, and then make a grocery list of what you need to eat during the week. Exercise is important for your body, too. To revitalize your look you might want to consider joining the community gym, walking in the mornings and after dinner, or taking up a team sport on the weekends. Something that gets you out and active is sure to have a positive affect on the way you see yourself. As far as the dark circles go, I'm sure there are millions of cosmetic products which cater to it. Google it and see what you can find at a drug store.
Best of luck.