Just pick one of the systems thats space combat for 20% and run it 5 times so no transit time (what you're already doing), maybe pick one with a radiation satellite so every other day or so you can turn in 300 radiation reports for an extra 30 marks. Or do the Acamar system with the clan diplomacy thing, and win or lose you only have to fight one wave of enemies instead of 5 (plus all the dialogue stuff), but it only gives 15% instead of 20% so you have to run it 7 times. And of course if you don't actually turn in the Sector Patrol thing till during the Reputation Event, regardless of when you actually run hte missions, its an extra 15 marks for free.
Of course there's always Epohh tagging, tedious as it may be.
If you pick the scan radiation daily on New Romulus, you have to scan radiation in the end of several system. And if you do them all, you also have your space daily. It seems best to do both at the same time.
I took this daily once, from the guy with the scan radiation tutorial. I didn't know about this quest before (I hate new romulus ground grind, and skip it as much as I can).