Yeah, phrasing it right wouldn't be trivial, but much easier than making wishes for UFAI, because Veritaserum is the equivalent of perfect box for AI, and Draco is human, so most of the definitions and assumptions he shares with the judges.
So maybe: "Tell me the things, you think I would want to know about, according to the best model of me you can construct."
With heavily leveraged trading on forex ( http://en.wikipedia.org/wiki/Foreign_exchange_market ) , he can make 100 galleons into 100 000 galleons in one hour (with leverage of 0.2% you earn profits from trading of X, but you only need to really have 0.002 of X). And you can do this over internet, by a few back and forth trades that lasts for a few minutes.
And there is leverage, so you can invest 100 $, but get profits or loses like you invested 10000 $. So if theres 100x leverage, and 1% profit to make on currencies each day, you can double your money every day.
So to turn 100 galeons to 100000 galeons Harry would need 10 transactions with 1% profit each.
http://www.investopedia.com/ask/answers/06/forexleverage.asp#axzz1qS7tVBFp