Its going to depend on how many leds you run on one circuit, when I did the lighting on my servonaut unit I bought a package with 500 resistors that ranged from just a few ohms to thousands(maybe $10 at radio shack). The calculations aren't hard at all to figure it out just have to know the voltage of each led(not sure what the mfu leds are rated at) and the out put voltage of the unit(I used 7.2V and everything works fine). I'm sure someone will chime in with the formula, I can't think of it at the moment.
I'm sure there are some mistakes, so hopefully someone straightens my mistakes out
J.D.