You should eat carbs prior to your run just as you do and having gu gel/pieces of bars during your run will supply fuel for your long run as well. This would be more important during the warmer months when you are also drinking a larger amount of water in order to replace some of the electrolytes while you are running.
The problem I see with gel/bars is that people who are not performing long runs (such as marathons) think they need to down a bottle of Gatorade. The amount of sugar in a 32 ounce bottle of Gatorade is enough to offset the caloric deficit from the time you just spent in the gym. We really don’t need these “fake” foods when doing the training prescribed here in this challenge because we are not running the risk of depleting our bodies of the electrolytes. These training sessions should only be lasting between 45 minutes (weights only) and 1:15 (weights plus cardio).
Having that handful of mixed nuts and fruit is great for providing a bit of energy between your resistance and cardio.