Upcoming Grand Arena player - asking for advice

Wampa will be difficult for me to get: I am in a guild all by myself (not including 3 inactive people) and most I can get from Territory Battles is 2700 GET (10 Shards per battle; will take 7 months to get Wampa). Admiral Raddus I think I can try getting, though the fact he isn't accelerated will make things difficult (I had to unlock marquee events on the day that the Raddus event ended).

What's a quick way to get 17 Zeta materials? Other than me needing ~12 more days to get a total of 20 Omicron materials, that's the only thing stopping me from getting an Omicron on Qui-Gon.

Are all players automatically pulled into Grand Arena when an event starts or do you have to manually join it? The phrasing of the Grand Arena introduction really seemed like the former.