Wow. You have your work cut out for you then.
So it will need a lot of things. You are going to need proper seats, because E36s have the seatbelt bucket attached to the seat frame. Almost any aftermarket seat does not have provisions for them, so you are SOL. Obviously you will need to buy the seat belt itself as well. Next thing you will need to do is buy an entire heater box assembly as you will need some sort of fan/defroster to pass a safety AFAIK. I am assuming all the lights and stuff work? Then the usuals, proper tires that have tread, brakes, etc etc.
Oh, and just an FYI, there is nothing M3 on that car except the steering wheel.