2 gallons of cider, if you fallow the directions on the back of my priming sugar cudes packages it two cubes for one 22oz bottle. One cube is equal to one teaspoon of sugar so two tea spoons per 22 oz... i would sugest three if you want a stronger carbonation. the direct math would be that in two gallons there are 256oz of brew... 256/22 = Tea spoons per 22, multiply by 2 for number of tea spoons total = 23.27 Tea spoons, there are 48 tea spoons in a cup so divid 23.27/48. This equals .49 cups (roughly half a cup) of priming sugar for a carbination of two gallons by package directions... You can add 3 tea spoons per 22 and that would require .73 cups of sugar (just short of 3/4 of a cup). This last sum is for a more strongly carbonated cider, how much i am unsure, havent tried it.
Note: this has been proven false, it seems that this is far too much and my directions are not ment to be translated into bulk calculations, but simply that the drops are ment to be dropped into the bottle prior to filling and dissolved during the bottleing process.
My priming sugar cubes are simple compressed granulated table sugar, bought them at the local Home brew shop and they work just fine. So simply put it in the granulated sugar. If you want to use brown sugar add slightly more (say 5-10% more) because brown sugar is sugar cut with molasses and that will drop the fermentablity of the sugar slightly because molasses is only about half fermentable. That should do it, good luck.
cheers