Complex carbs are great to eat, as is protein and fat.
Make complex carbs, complete protein sources (meats, dairy products, supplements etc)and fats a part of your regular diet.
Brown rice is an excellent source as is quinoa. Eat oatmeal, whole grain pastas, whole grain cold cereals etc with every meal if you are running often. (and pushing yourself for improvement)
A few days before an event or big trial run, up your complex carb intake. The night before and morning of the run, definately eat lots of simple carbs. Eat simple carbs as you run too. The little goo packets, gatorade, powerade etc are great sources of necessary simple carbs.