Find a group on Nukara. Do NOTHING ELSE except rescuing redshirts, closing the portals, collecting tholian science reports, and killing Tholians.
During the 2 hour gathering event, a good group will net you 6-700 fleet marks by the end of it all, but it does require you to be pretty on the ball about turning in missions and getting it again.
"My frozen dairy-based confectionery attracts all the males of the species to the facilities. They all agree on it's superiority. Indeed, it is superior to yours. I could teach you the finer details but that would require monetary recompense on your part." -The Milkshake Song: Vulcan Edition
Head over to Defera invasion zone team up select ALL THE MISSIONS do the hard ones and then split up and take a zone each for the easy and meds 500 marks an hour is achievable plus you get omega marks ... everytime you die or are near basecamp collect and restart the missions.... do not even bother doing the hard probe mission it auto completes if uyou have it running anyway