If you're new and must have a certain kind of weapon that costs Energy Credits, try to get into a few PvP matches. They include Energy Credits as part of the reward for participating, even if you don't win. Lower level Federation-side PvP isn't too bad when the queue is moving.

If PvP scares you for some reason, you can farm data samples in exploration zones. A single rare can be sold on the Exchange for decent credits.

Just some suggestions. I know a lot of people won't buy anything with EC until they hit VA1, myself included. But do what you'd like!