When you say "jumps" I assume you mean trade gates and not jump gates. I've got a couple that I use when I want quick cash without too much hassle.
Planet Manhatten -> Planet Pittsburgh = Pharmaceuticals
Planet Pittsburgh -> Planet Manhatten = Boron
Using a Rhino, you make about 2000 credits each way. It's a good, safe, run when you're starting out.
Planet Curacao -> Kingstone Border Station = Water
Kingstone Border Station -> Planet Curacao = H-Fuel
The water just gives you a little return for the trip back, the real money comes from the H-Fuel. This requires a stronger ship than the Rhino, as Cruise-Disrupting Corsairs and Liberty Rogues attack the trade lane intermittently. My experience is that they'll attack in force the minute you put all of your money into a load of H-Fuel.
The beauty of the Curacao/Kingstone run is that it's one jumpgate, and one trade lane, a quick and easy run. If the trade lanes seem to risky, you can also run the route with cruise engines, as it's only about a 35m trip. Just make sure to steer clear of any enemy you spot along the way.
Note: I'm in no way endorsing these two routes as the best there is. They're simply two that I happened upon and made use of. They helped me in time of need, until I could afford a big boat for the longer, high profit runs.