Assuming you have no 100% eido, Dark actually looks like your best team atm, but it's pretty hard to recommend any investment into dark until we see some light down the tunnel...
Your thunder is decent, but not particularly amazing. Water and Fire is pretty basic and not really worth mentioning.
Basically, you're free to pick what you like. Maybe focus on an element where you have the best grid, and determine your own future. Unfortunately, it's pretty hard for me to recommend something meaningful in that regard without knowing more about your account (how old, what you have, what you missed, eidos/grid wise etc...). So as a general fallback, maybe look into light since there are a lot of really strong/useful himes there (Sol/Michael is a good start).