Yes, Trump will use his presidency for personal gain. Mr. Trump's entire adult life has been spent in pursuit of personal wealth, and there is no reason to believe that his time in office as President of the United States will be any different. His failure to disclose his tax returns during the campaign and his apparent disregard for federal ethics rules have made it clear that Mr. Trump does not consider himself bound by the rules of convention or by legal restrictions. Mr. Trump has remarked on his own personal greed; he is unapologetic about it. There is every reason to expect that Mr. Trump intends to use his position as president for his own profit.
The fact that he is already putting pressure on diplomats is an indication of how things will be. To be successful in business you need to see opportunity every where. The business culture Trump is from is founded on exploitation. It is natural to assume that this type of exploitation will continue.
When Clinton was Secretary of State, the Clinton Foundation received massive donations from people all over the world. Chelsea used these donations to buy an expensive place to live in New York City. Trump will do the same things while President for his own personal gain. All politicians do it.
Trump is already using his presidency for personal gain. There have been reports of deals that he has made in other countries that have happened since winning the election. Trump is the kind of person that will do anything he can to improve his own personal wealth and power, and being the POTUS is the perfect way to do it.