fire phantom thief is very good.
water mystical witch is useful in arena
fire magical archer is not bad, and she can be used for fusion later in game
wind living armor can be really powerful when it reaches 6*. keep it for now but early on, he's quite useless
fire hellhound after awaken has really nice buff
water warbear after awaken nice self-revive, great to be used in dungeon/map sometimes
water werewolf disturb heal & can heal team. good tank as well
water fairy is good disabler/healer after awaken

i would suggest to focus on below by priority:
fire phantom thief
fire hellhound
water mystical witch
water werewolf
water fairy
wind living armor (keep for now but no need to focus on him)