I am really confused. My wife does not satisfy my physical needs easily. My friend gave me horrible advice. In India there are some tribal people (non-Muslims) who sell their daughters. My friend told me that if I buy a woman I can have sex with her without marriage. Is it true?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Allah has permitted only two ways to satisfy one's sexual desire, i.e. through marriage or through the slave women one possesses. Allah Says (interpretation of meaning) in this regard: {And those who guard their chastity (i.e. private parts, from illegal sexual acts) except from their wives or (the captives and slaves) that their right hands possess, for then, they are free from blame; but whoever seeks beyond that, then those are the transgressors;} [23:5-7].
The advice of your friend to satisfy your sexual desire is a transgression, since it is neither through marriage nor through slavery, which are lawful in Sharia. The 'Asl (basic rule) in Sharia is that all children of Adam (Alaihi al-Salaam) are free, no one is liable to capture them except when they have a reason to be captured.
A father selling his Kafir daughter is not a reason to make her a slave. Yet, if a father has a slave daughter from a slave woman and then the father purchases his slave daughter, by possessing her she becomes free, and no one is permitted to purchase the daughter from her father. Because the majority of Muslim scholars, if not all of them, are of the opinion that if a person possesses his/her slave father, slave mother or slave forefathers whether they are males or females, automatically they become free merely by his/her possessing them. The same is true regarding his/her slave children and their descendants whom he may later possess.
Allah knows best.