poison - water main

shields/clear/immunity or control - fire main

extra standards or control - lightning main

Pick the main with mystery you want to use.

I would * with earth main for def/res + shields + atk/nin boost

2nd choice would be fire main with the shields/clear/immunity mystery + nin leech + chakra boost

*edit: I forgot wind main. I don't use her much...at all, so no opinion, sorry