Proof of reciting prescribed azkaar by the Mashaayikh

Q: There are some specific prescribed Zikr by the Ulema and Mashaykh which are called "Wazifa". These are certain Azkaar of reading a Dua, or Ayah of Quran or the names of Allah for a specific number of times in order to achieve something. 

My question is that, do we have evidences from the Quran, Sunnah and the practice of the Salaf on practicing these prescribed Azkaar? Can you please list them in detail with references.

Adding extra money for one child so that the investment for both children will be equal

Q: I've got two sons. They're toddlers. 

My elder son received alot of money as a gift when he was a baby while the second one didn't receive as much. I was thinking of converting their cash to gold. Will it be okay for me to give money to add only to the younger one so I can get the same amount of gold for each child or will it be unfair to the older child? 

We will not inform them of this when they are older.

Dealing with people who tarnish your image

Q: How to deal with people who lie about you, tarnish your image, hurt you and deprived you of your basic rights. They constantly taunt you and pick faults in you? How to stay firm in faith when you see a liar and deceptive people to be successful in life while truthful and honest ones suffer? 

Is continuously praising oneself and thinking low of others permissible in Islam?

Trading gold on the forex market

Q: I have recently heard of a new venture many of our Muslims are going into, it is the trading of gold on the forex market. I wanted to find out if it is permissible and if so then how, as no physical exchange of ownership takes place, and also if you own an item although it can depreciate in value it won't cease to exist as is what happens on this gold market.