@OP,

i suggest you build a team around Water. Ryu-oh is a top tier SSR hime in water lineup and the water element is F2P friendly. then u can build a wind team around Gaia as your backup element, in case your water team run into problems against Thunder events.

for mtix, i suggest the following priority: Vohu Manah (after Feb 2019) > Ashera > Snow Raph > Aphrodite