I don't know about anyone else but i do all the dailies. These would be Illum(money and classic comms), Black Hole(money and classic comms), Section x(money and classic comms, makeb(money and basic comms), cz(money and basic comms).
If you clear all of the dailes u can walk away with between200-400k credits per day-(rough estimate)
In essence you can skip Illum, Black Hole, and Section x if you have no need for classic comms
What i did was i did all the makeb dailies as well as the fp quests that grant you basic comms as a reward. I saved them up for a few days and boom piece of gear. Now with the implimentation of czerka, you can get more basic comms faster(as basic comms drop off mobs in czerka).
so in a nutshell do every makeb daily,every czerka daily, the czerka fp quests and u will net basic comms quick