most people say 300 over maintenance, and add 300 a week, (or tailor calories towards lbs. gained per week/ 2 weeks/ month w/e.)
And on diet yes if you are not a hardgainer and you want quality mass it needs to be clean.. you will eat a lot of the same things as cutting except basically add larger portions and dont be afraid to incorporate "heavier"/ dirtier meals such as mac n cheese, spaghetti, pasta, steak, whole eggs and whatnot. These things are a little dirtier than what you would eat while cutting but still decent by all means