You might know about the trading that goes on the Internet. We purchase a commodity using our bank accounts in USA. The thing never reaches us, and then on the fluctuating market when the prices go up we sell it for profit. In this whole process we never get the stuff we buy. All we do is online trading (simple we never have to leave our place in this whole process). The commodities are mostly currency, gold, oil, sugar, etc.
I had a discussion with my father who thinks this is not Halal earning. While my thinking is that as long as we are avoiding alcohol and other Haram stuff this is Halal. Please tell me is it Halal or Haram in the light of Shariah.

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

Buying any commodity before looking at it or knowing its description in detail so that it becomes known and that you no longer have any confusion about it, is not permissible as to avoid getting into any future disputes or risks in that contact.  It is also not permissible to sell any commodity before taking its possession for the Hadith of Hakeem bin Hizam that he said to the Prophet (Sallallahu Alaihi wa Sallam), ‘O Messenger of Allah, I purchase many sales, what of these sales are permissible to me and what are forbidden’.  The Prophet (Sallallahu Alaihi wa Sallam) said: “O my nephew! If you purchase something do not sell it before it  is actually delivered to you”. [Ahmad]  Imam Abu Dawud reported from Zayd bin Thabit that “The Prophet (Sallallahu Alaihi wa Sallam) forbade to sell the goods in the place where they were bought until the tradesmen take them to their houses”.

Therefore, the procedure of trade you mentioned in your question is not permitted.  It is compulsory to take possession of the purchased commodities yourself or by your agents before selling them.

Allah knows best.