Gels work well with bars. The bar will give slower, long burn energy. The gel will keep your sugar levels high. On a five hour ride you might have one or two bars and three or four gels.
One great gell is Enervit. It tastes like a flat, concentrated Coke. It has lo lot of sugar so it is best towards the last part of your ride. I always keep one on me just in case. "Break in case of emergency"