Drywall
You should remove mold and mildew from the ceiling before beginning to repair it. A stain blocking primer such as shellac is also an option. When you're done with patching you can start painting over the stain. This might sound difficult but you have many options for ceiling textures.
Plastering a ceiling is a tedious task. Plasterboard patches are an alternative if you don't have the skills to plaster a ceiling. You may need to redecorate your room if you use this method.