I keep it simple. Water and Gu. That will get me through 1-2 hours of whatever. I'm not a big fan of sports drinks but I will sometimes use them during a workout or race if they are provided and I feel like I need them (especially if I am sweating a lot, which I usually am!) For longer workouts, I'll put a protein bar and a banana in my jersey pocket or my bike pack, since I'm mainly doing only long bicycling distances these days. That will get me through 2-4 hours, and then I treat myself with a good hearty meal!
For supported training and events (I trained with TNT for my first and second half marathons), they usually provide Gatorade and pretzels every few miles. If you are like me and sweat a lot, take advantage of those -- I found out after one warm and humid 9-mile run that I really need to replenish salt!
One tip: don't do Gu and Gatorade (or the sport drink of your choice) together. At one stop, have a Gu and water, and alternate so that at the next stop you have Gatorade.
I prefer to carry as little as possible, but you will figure out pretty quickly what works best for you. Kudos to you for training for this! You'll be glad you did!