Yeah, I am a fan of yukon gold potatoes for most applications, but when doing gnocchi, it is russets all the way. The starch is necessary, and the key to keeping them light in my opinion is to not overwork them once the flour has been added. All the other tips people are saying are right on the money, though I never knew of the strict importance of letting the potatoes cool all the way before working with them. My darned impatience always had me adding ingredients just as they were "cool enough" to work with, and so that the egg would not "cook" as soon as I added it to the hot potato mush.
So I learned something as well, and will let my riced potatoes spend more time in the walk-in before I proceed in the future!
Oh, and another tip - when you are making them, have a pot f slated boiling water going. Make 2 or three, and then test them out in the water. Sure, you have not frozen them, so this is not "ideal", but it will give you a sense if you have added enough flour, or overworked them or seasoned them properly and so forth. Basically, if there is an error in your batch, you can rectify it as you go instead of churning out a whole batch and THEN realizing you messed up.
DeglazedMy Continuing Journey Into the Kitchen...