If you want to earn money, don't fly to Europe and Hawaii yet. Wait until you have around 15-20 million DOP.
use gate search to find gates near Midway, fly to as many as possible nearer than 500 miles. This will increase your DOP very fast. Purchase new planes and repeat.
I think the ATR 42 is a good plane to start with; when you move on to jets I would choose Fokker F28 and/or BAe 146.