To magicpea.

I second everything Sanahtlig has recommended you. I think what hasn't been mentioned enough yet is just how powerful a 100% eidolon is. It is by far the single biggest boost you can give to a team. If you get a 100% eidolon you really should put together a team for that element. Thunder is quite respectable later on and has some very strong himes so if you want to keep investing in it Thor is certainly a good choice.