Only dry spices. I used to grind fresh ginger & sometimes herbs -- not a good move. Eventually the moisture gets into the interior. Use a mini food processor for fresh ginger or grind by hand (the Japanese graters with the little teeth that hold the stringy bits back are excellent) & mix your ground dry spices into it.
Cloves and nutmeg tend to be damp when ground. Adding a little sugar or flour into the grinder helps make them easier to grind. But you definitely shouldn't try to grind fresh ginger in one of these things. You can get a cheap hand ginger grater at any store that sells Asian cooking supplies.