Wait until the end of free draws, then choose either Titan, Varuna or the Sunlight Stone depending on your results.
Earth and Water are pretty viable F2P though, I wouldn't exactly call it watered down. Sure, Murgleis and AK-4A are insanely good, but your base grid is Fimbuls and Auberons or Baal Axes anyway. You could also make a case for the magna dirt grid being as strong as primal earth, specially with Magna II in the near future, but I'm not seeing magna II saving wet from dagger hell, and assuming you get enough Ancient Auberons for a viable magna grid, you will probably have enough normal ones for a Primal Water grid, so Varuna is a straight upgrade either way