How to avoid poorness?

The richest people in the world make money from financing & conducting wars and similar evils, such as slavery, usury & exploitation. The teaching in MN 135 that giving leads to riches is false. Throughout history, the richest most materially wealthy people have been warlords & other evil mafia thugs. 35% of Forbes 400 are Jewish, which shows Buddhist MN 135 does not lead to wealth. In MN 135, the word for "wealth" is "bhogā", which appears to refer to "material wealth" rather than "spiritual wealth" ("dhana"). That MN 135 was supposedly spoken to a Brahmin student and not to Buddhists shows it is fake dharma. The best way to be materially wealthy is engaging in wrong livelihood, such as selling drugs, alcohol, gambling, sexual movies, loans, weapons & other evil vices and mining the mineral resources of the earth, such as oil, gas, coal, iron ore, copper, etc. Another way to be wealthy is to start religions and offer salvation in heaven in exchange for donations.

Of course, if one resists far away from the possibility to give into more Sublime, such does not mean "he/she does not give to brahmans & contemplatives". In how far such is a valid reasoning for one, one has to prove by oneself honest, if wishing no disadvantages from certain habits.

"I tell you, Vaccha, even if a person throws the rinsings of a bowl or a cup into a village pool or pond, thinking, 'May whatever animals live here feed on this,' that would be a source of merit, to say nothing of what is given to human beings. But I do say that what is given to a virtuous person is of great fruit, and not so much what is given to an unvirtuous person. And the virtuous person has abandoned five factors and is endowed with five. (on giving)

For one desiring wealth in the future, aside of Sila (virtue, which is the more secure way), generosity toward proper and sublime objects is it's effect. If one is capable to manage giving to proper recipients, maintaining Silas, such is unexcelled in regard of future wealth, if desired.

"But then there is the case where a woman or man is a giver of food, drink, cloth, sandals, scents, ointments, beds, dwellings, & lighting to brahmans & contemplatives. Through having adopted & carried out such actions, on the break-up of the body, after death, he/she reappears in a good destination... If instead he/she comes to the human state, then he/she is wealthy wherever reborn. This is the way leading to great wealth: to be a giver of food, drink, cloth, sandals, garlands, scents, ointments, beds, dwellings, & lighting to brahmans & contemplatives.

One might think why not the case when giving toward equal or lower. Because such is actually the ordinary way, everybody gives to what is near or beloved, or target to get under ones control. Where ever one gives into, there one is destined.

Like if one praises the common and lower would not increase his value under those more sublime, one devoted to scarifies toward equal or lower increases or maintains those bonds.

Or let my person give another sample: Like a worker or servant of a lord would never climb up in his position, gains no remarkable reason to get opened a door, someone not giving toward higher, is bond to be left off.

No misers go to the world of the devas. Those who don't praise giving are fools. The enlightened express their approval for giving and so find ease in the world beyond.

— Dhp 177

Mudita with all who could and will trace their own and valid worthy objects for their scarifies and may no one ever misses to recognize such for their future well-being in wealth.

(Note that this is not given for any trade, exchange, stacks or entertainment binding to equal or lower, but for upward and liberation)

Piya Tan writes of this sutta,

The Cūla Kamma Vibhaṅga Sutta is special in that it gives some specific examples of the fruits of karma, good and evil, based on the simple folk notion of good begets good, evil begets evil. Clearly this discourse is addressed to the lay community, especially those not yet familiar with deeper doctrine of karma in the light of not-self. Significantly, here the protagonist is the brahmin youth, Subha Todeyya,putta

... and ...

The teachings on karma here is one “whose meaning needs to be drawn out” (neyy’attha), unlike, for example, the Assu Sutta (S 2:179 f) whose meaning is directly apparent (nīt’attha).

See also What are 'suttas of indirect meaning' in the Pali canon?

The whole sutta is in to answer the youth's questions,

Master Gotama, what is the reason, what is the cause, why baseness & excellence are seen among human beings, among the human race? For short-lived & long-lived people are to be seen, sickly & healthy, ugly & beautiful, uninfluential & influential, poor & rich, low-born & high-born, stupid & discerning people are to be seen. So what is the reason, what is the cause, why baseness & excellence are seen among human beings, among the human race?

... with the answer being ...

beings are owners of kamma, heir to kamma, born of kamma, related through kamma, and have kamma as their arbitrator. Kamma is what creates distinctions among beings in terms of coarseness & refinement.

The Sigalovada Sutta (DN 31) describes how laypeople might manage wealth appropriately.