Also an additional way to boost your Fleet Mark income is the use of Fleet Marks Boosters. They pool an extra 100 Fleet Marks and boost your regular Fleet Mark income by 20% (or at least 1 Fleet Mark) until they are depleted. Those Boosters cost about 15k Fleet Credits, if I recall correctly, and are available in the Requisition room.
As for Commodities, I am frequently opening my Tuffli to the Fleets, so you can buy them really cheap. If I am not available, there might be other Tufflis available on the "Public Service" channel and if they are not, then the Trader near the Kei System (right next to Sol) is your choice. Check out the prices here.