He is dressed entirely in black: a black T-shirt, black leather pants and black boots.
I'm not entirely sure what you mean by "a comma should be placed after the final word/phrase before the end", but I'll assume that you're talking about using a comma before "and".
This is called the "Oxford comma". It's optional: some writers prefer to use it; some don't.
Don't worry about it; it's a free choice. Do whatever you feel comfortable with.