Creation exists in layers
We know that on the amavasya of the month of Kartik, Lord Ram returned to Ayodhya, which was marked
To give an example of a Diwali practice, ‘ya devi sarvabhuteshu shakti roopen sansthitha, namastasyei, namastasyei, namastasyei namo namah’ is the mantra which when channelized by one’s Guru, and chanted while keeping awareness of the name, form and shakti of the devi while fixing the gaze on an object or image or thought (as prescribed by your Guru) endows the practitioner with phenomenal glow and radiance of the devi, such that he/she can attract whatever he/she desires in the physical or the world of energy. The mantra however must be given by and practiced under the supervision of your Guru.
Diwali is the night of acquiring siddhis and powers, wealth and riches are siddhis of the physically manifested creation. With time, the sadhnas of Diwali distorted and people took to grosser forms, like gambling, for acquisition of wealth.
In earlier times and for those who have a guru, if there is a desire for wealth, there is yogic process which has to be followed but unfortunately in modern times when most dont have gurus, a distortion has set in in the form of gambling to acquire money and power.
Remember, Diwali is the night when Ram came to Ayodhya. It is the night to bring Vishnu to you.