swgoh.gg has meta team reports, and is a good resource, but since you are new it will show mainly GL's etc. EP(lead zeta) vader (with merciless zeta at least), thrawn dbast + 1 (tarkin maybe bc of his ship, not sure where you are on that, unless you use thrawn's ship) is a pretty good team. You should also think about farming the bugs, for both arena and ships.
guild store look for ewoks, there are some that pop up (wicket/paploo/logray, not sure which pop up)
Vader shards only come in small bunches from achievements, and are sometimes available in the stores iirc(can't remember which, sorry)
you should transition to empire/sith or bugs as soon as you can probably. try teams out and see how it goes. Geos will also get you to padme, which is a much better long-term arena team than empire or bugs.
try and get some high level allies so you can beat tougher missions to get the rewards (regular, cantina etc)
glgl