Last month I increased my net worth by 4k gold (that is after buying goodies for myself, although I haven’t really made any expensive purchases in february.) I’m aiming for 5-6k+ gold gained this march alone.
I spend about 2 hours in the game per day to manage my investments and research new markets, and track them throughout the day with my nifty spreadsheet. My markets change almost on a daily basis depending on what’s profitable at the time, but when you start having large sums of money, making more is not hard at all, even without ugly market manipulations.