The cocktail that I use to fuel my long runs is a mixture of Gatorade (the powder not the stuff in the bottle), table sugar, and salt. Sometimes I throw caffeine into that mixture, usually if I will be running for 2.5+ hours. I prefer mixing my own drink as opposed to using a prepackaged gel or beverage because I can craft it for that specific run. It is also cost effective to mix my own.
In terms of the amount of carbs to use, I recommend 45-90g of carbs for every hour after the first 60 minutes of running. Of course someone who is larger will need more carbs than someone who is smaller, and someone who runs faster will need more carbs per hours than a person who runs slower.
In my cocktail I aim for a 2:1 glucose-to-fructose ratio. A 2:1 ratio seems to be optimal for replenishing muscle glycogen and liver glycogen. The Gatorade powder comes in a 3:1 ratio and table sugar (sucrose) comes in a 1:1 ratio. To get the mixture to a 2:1 ratio, I use two parts gatorade to one part table sugar.
For example, if I use one serving of Gatorade, that is 24g of sugar. Since it is a 3:1 ratio, it has 18g of glucose and 6g of fructose. Then the one part of sugar will be 12g and since it has a 1:1 ratio, that means it has 6g of glucose and 6g of fructose. Combining it all together we get (18g +6g) of glucose and (6g + 6g) of fructose, which gives us 24g of glucose and 12g of fructose. And there we go, a 2:1 ratio of glucose to fructose.
I add the salt to make sure I am replacing the sodium that I am sweating out. The Gatorade comes with sodium, but not enough. Depending on the individual, one can sweat out between 500-100mg of sodium per hour. I usually recommend adding 500-800mg for a two hour run. Of course if you still have signs of low sodium, then you may need to add more.