I've realized that it will be vaible to keep Duo gear for a duo build and tri gear for a tri build and just level all spells to max. This is likely what I'll do and take build according to instance, though I will probably go mostly tri to begin with due to the time it will take to level all spells.
Basically, WATER GOOD. Everything else, average to mediocre. You need something to trigger Water's secondary damage and that's about it.