In all honesty, I don't think he has a "strategy". But supposedly he purchased $5,000 worth of the Iraq currency from some website.
I guess the strategy would be summed up from this simpleton blurp from an article in Boston Magazine:
"Not long ago, the Internet buzzed with rumors that Donald Trump had sunk $30 million into the Iraqi dinar. The fact is, most serious investors wouldn’t touch the stuff. Those who do are generally average joes, people who plow no more than a few thousand into their portfolios. The abiding hope among such investors is that as stability returns to Iraq, its currency will be revalued—perhaps even reach parity with the dollar. If that happens, the Nebraska housewife with 800 bucks’ worth of bank notes stashed beneath her bed would wake up a millionaire. It’s this, the possibility of an abrupt and staggering windfall, that keeps people coming back for more."
http://www.bostonmagazine.com/articl...ful_of_dinars/
My friend maintains that since the "world powers have billions invested in Iraq" - they will ensure that, over time, the country remains stable, becomes democratic, and the currently will stabilize.