When does your energy pool empty

[IshmaelProphet 0]

For example, you only have two energy, can you rest two energy then attack with SSGSGoku, ready one energy then rest it to pay for a 3 energy cost battle card? Or does the energy pool drain once I attack?

[RPENERGY 8]

There is no "pool" so to speak. You exhaust your cards in your Energy Area to play other cards. If you have a 2 cost in your hand, you exhaust both of your energy to play that card.