The game doesn't tell you what energy is for. I have a reactor, a battery, and a tech to boost energy generation, but nothing seems to need energy?
You cannot see the stats for items when picking loot after a battle. This is bad because there are so many land types and some are outright worse than others (heavier for the same or less HP.)
As others have said, Floatrons just seem to be too rare. The shop is something of an answer, but you pay more than just money in using the shop. You also give up the chance to go to another location that would have given you additional free loot (which might have been some valuable non-floatron items.) Maybe it wouldn't be such a bad trade if you could sell your unwanted items in the shop, though that might end up devaluing the forge..