Get the Impact Grenade and Ion Torpedo
One of the first Star Cards you should definitely invest in is the Impact Grenade. It does a little less damage than the Thermal Detonator (another grenade), but it gets the job done in terms of catching your enemy off-guard and damaging multiple enemies at once. Since your Hand will be empty when your first start out in the game, the grenades will prove to be really helpful in terms of dealing damage in the field.
The Ion Torpedo is another Star Card you can get relatively early in the game. Think of it as a missile launcher that comes in handy when you’re dealing with an AT-AT, AT-ST, or other big vehicular powerhouses.
Again, remember that these Star Cards have to undergo a cooldown period each time you use them. Use them wisely to turn the tide of a battle.