Yama Deepak

Not sure if it's the right flair but here come the questions - What oil is supposed be used to light a lamp for Yama? In which direction is it to be kept? What material is the lamp supposed to be made of? We are studying Death and Afterlife at uni and I wanted to light a lamp during each class. What are the possible substitutes for all of these? I have the following with me - clay, steel, and brass diya In oils I have - sesame, castor, mustard. I also have ghee. Mustard smells a lot in closed spaces and folks in US are not used to the smell.