The best practice is to put 5 wicks – East, West, South, North & North East. and start lighting the north east direction first and continue, clockwise direction.
Use ghee to light the vastu vilakku for the first time, and can be use any oil subsequently. the five wicks represents five elements in the vastu, like Aaadhara Shakthi, Moola Prakriti, Aadhi koormam, Ananthan & prithvi.