The example of those who spend generously of their goods and possessions is like a grain of corn which grows 7 ears and each ear has 100 grains. Allah multiples the wealth of whomever he chooses and he is generous and the All-knowing.
When one spends on his own soul, he is making investment in his moral and spiritual development. Reading Allah’s final revelation, and following the dictates contained within, is the good way to spend on our souls. When we spend in the way of Allah, and perform the pilgrimage, or when we fast during the sacred month, we can earn 700 times more than just performing dhikr (remembrance of Allah) and it has a greater impact on our soul.
Attainment of material possessions, like clothing, housing and cars are necessary but they are not the kind of spending that is good for the soul. We have to be charitable to ourselves, our families and others, but we also have an obligation to our own soul.