If the queues are popping, PvP. Good cash (EC), skillpoint, and marks to be had, win or lose. Do this while farming for cash / replaying missions and you'll have more money than you can spend. Just don't be one of "those guys" that zones into the PvP match and sits there without doing anything. Go help your team. If you're afraid of trash talking, invite your teammates into a group and shut off zone chat. And have way more fun than clicking on data samples exclusively. Break up the monotony
Queue time depends on rank ... and server time. But you can generally earn huge sums of EC by PvPing while doing whatever else. The reward for participating in PvP is nothing to sneeze at if you need money. Even if you lose, you get paid, and it's probably the best way to earn EC that doesn't involve data samples and the exchange.
If you've never done the PvP thing, once a battle has ended you'll get an immediate reward that includes a bunch of energy credits. There are some videos on YouTube that I'm sure interested parties can discover if they'd like.
not sure what this would fall under, but I find when a new aspect of the game comes out that requires something you can make a ton of EC with lazy people who do not want to do the work for it. An example is those damn Jumja sticks O'Brien wanted. People were itching to get Diplomacy points when the new system came out. You could literally sit at DS9 and put those things on the exchange for a boat load of EC, like crazy amounts, and watch them get snapped up. Now not so much. I guess it could fall under following trends in the game. I think one of the next ones could be the skill boosters. Right now Q gave out a ton of them so everyone has them who did that game. But they are going to be used up quickly and I hope become more rare on the exchange.