@Fauztin gave you a good answer. You’ll need different teams for different areas of the game. Broken down by area,
For events, you will need Phoenix, Rebels (Phoenix are also Rebels), Rebel ships, Empire, First Order, Jedi, Nightsisters, Ewoks, Bounty Hunters, and specialty teams for Luke’s and Rey’s hero’s journeys.
For territory battles, you’ll need Phoenix, Rogue One, Rebels, Bounty Hunters, Imperial Troopers (also Empire), Empire, and 5 specific characters for each side (10 total).
For the sith raid, you’ll need pretty much all of the above.
And for arena, you’ll need to be paying attention to the latest characters and seeing if they can help you win. You can either choose to do what others in your arena shard are doing or run teams that can counter those teams. The developers are trying to diversify arena, so a few different teams will work.
