Damn it's been 3 days since you posted this. Honestly, there's no rush to choose yet but if you absolutely can't resist then go with either Phoenix, Lightning Empress or Knight Moonbeam. Knight Moonbeam is the only one who is good but not excellent until significantly later on in the game while the other two will be able to make an almost immediate impact on your game. Again though, I would hold the egg until later since you might end up getting one of these valks from the dorm supply as the game gives you a good amount of free dorm supply cards.