First, what are your other (Rs ans SRs) wind kamihime ? Oberon, Cybele, Zephyrus are quite good even if they're not SSR.
And yeah, you should focus on a single element, to be able to clear ragnaroks as soon as possible. try reading the FAQ, it's very good.

Yeah, you get SSR Eidolons for each event. That said, there are 3 event types : advents, raids and unions.

Basically, in advent events you get materials that you can exchange for rewards (SSR eidolon, SSR weapon, SR weapons, books, soul points...), in raid events you get rewards when you reach thresholds of events points + you get event gacha ticket, and in union events you get rewards when you and/or your union reach thresholds of events points.

You want to get in an union asap, as there is an union event starting in a few hours !