How many lights we can use in a lamp for daily pooja?

Hi all,

I am very much confused for deeparadhana. How many lights in a lamp we need to lighten up for daily puja and what was the meaning? Some people doing with one light in a lamp, some with 2 and some with 5.
Recently I met one lady she was doing one light in a lamp but for one light using 3 bathi. She said I am using 3 bathi in one light for 3 main gods lord Brahma, lord Vishnu and lord Shiva.

Any one please helps me, how many lights we can use in a diya for daily pooja. And what was the significance.