If you going to work a double, you need to work a double. 13 hours is 1 hour more than one shift. In reality, you worked about 12 hours to make lease and gas, one hour for yourself- which is about right for a newbie doing a 24.
The trick is to work about 20 hours of the 24, but sleep when it is slow. For example, on a Saturday double, you try to pick up the car early early early Saturday morning, then around 6am even go home and sleep for 4 hours, then get back up around 10-11 and work it hard until about 3 am Sunday morning. You should be able to pocket 400 for yourself.
Also, make time not money. Always take the quick way, even if you have to eat the toll. By 5pm, you should have lease and gas. That means the next 10-12 hours is for you, and at 30-40/hr, you should be able to bring home 300-400, more like 400 this time of the year.
Also, any dropoffs at Penn or Path or Grand Central ask them where they are going, then ask if they would like to be taken there by you, if the traffic is good at that time. 80%-90% of the time they will say no. 10-20% of the time they will say yes, but those yesses are nice long trips, and the 80% no's cost you nothing.
So, don't complain about this being slavery if
1) You are not willing to work hard
2) You are not willing to work smart.
Good Luck,
Antolin