If you have trouble getting the Energy crystals you should go to Battleship island located in the corner of the map. You can't see the island on the map however. Just search for a bit in the corners and you should find it. Get there with the Ragnarok. In the island you will see a blue pillar in the midle of a room. stay still as the pillar shine and go towards it when it does not. When you reach it you will get questions from Bahamut. Each time you answere you will encounter a Ruby Dragon and each time you chose the wrong aswere you will have to answere the question again. The last answere is hidden. You will face Bahamut and if you beat him you will get him as a GF. He has an ability called Rare item. When that ability is equiped you will obtain *rare items* more easy. You may also get some Crystals from the RDragons.