I've never seen a possible way to have econ issues unless you're, say, on Broken Golems or Spirecraft Medium. Early in the game your econ sucks unless you get better harvesters, in which case it is so overwhelmingly good that you can't possibly spend all of your money barring extremely expensive bursts of building basically an entire army. But then, energy? I have absolutely never had to ever have a matter converter. This is probably because the highest I have ever gone is difficulty 7, and typically there, you can take many more planets than on other difficulties. Each planet is 150k energy, though, and that scales stupidly quickly... especially when you get enough income to get matter converters and still have income to spare.
People who are higher up need to testify as to exactly why they must be so low on energy and stuff, because I don't really understand how it happens.