Any advice for making an application portfolio?

hey guys,
i’m currently a freshman in ID in China,just thinking about getting enrolled in school in US next fall. I’m applying for several schools now so I really need some advice on my portfolio. my questions are as follows.

What kind of paper to use ? A4 or what size?

how about the holder?

since i have to send each school a portfolio, so copy pieces will be alright?

what exatcly do i need to put in my potfolio?

i have many black and white sketches of real cars and other still objects, should i put some good ones in my portfolio?how many should i put in?

Since i haven’t got many designs of my own, i wonder how much emphasis they will put on my designs?

i haven’t learned 3d modling,so i can’t put 3d renderings in the portfolio will that be a problem?

Thank you for any advice or suggestion! need your help asap! i’m so longing to go to US! ur precious advice will gonna help me realize my dream~~