Assuming your Silver, the Increased EC Cap is a wise buy.
VA ships are another good one, since more and more upcoming content is focused on end game, you will get long use out her.
Most of all, Items that unlock for your Account, rather than just a character.
do you have plenty of inventory space? that always comes in handy. same with bridge officer and doff slots. i highly recommend a full crew. these things are constant. ships come and go. there will always be new ships coming out.