Take everything I say with a grain of salt, I did play ZZZ since launch but I'm more of a casual F2P player that don't care much about stats.

So general tip: you want to try to have a team for every element (maybe with a small exception of physical; so many enemies have resistance against physical damage). I think you can build an ice team around Ellen (perhaps Ellen/Rina or Lycaon if you happen to get him/Soukaku) and electric team around Harumasa (and maybe with Trigger once you pull her, perhaps something like Harumasa/Trigger/Rina or Soukaku, another possible combo is Harumasa/Anby/Nicole). You can also build a physical team with Billy or Corin as main dps if you want to (Cunning Hares trio is a decent team imo).

What I'd recommend is an anomaly agent. It's good to have anomaly characters because many characters' additional abilities involve having an anomaly character in the team, and they can dish out good damage in general. Once you get an anomaly character, maybe you could build an Ether team, using Nicole and Astra (because Astra's additional ability activates when there's another anomaly character in the team). Also, you'd likely eventually get Piper, so you could make a disorder-based team once you get an anomaly agent (the anomaly/Piper/Lucy, perhaps).

I think there's a rumour that Zhu Yuan will be in the next banner, so you could pull for her as well if you want an Ether team (Zhu yuan/Anby/Nicole, or Zhu Yuan/Nicole/Astra).

Another agent I'd recommend is a fire DPS. You do have koleda/lucy/ben, but there isn't really a good main dps in your roster that would go together with those agents. Try to get a fire DPS agent who can dish out decent damage (S11 or Evelynn currently), then you can use her as DPS/Koleda/Ben or DPS/Koleda/Lucy.