Each soldier class has a specific task. Some perform better when out of the mission area, while others will give an advantage when they rush in. You must have a balance between each class for the current task. Heavy Gunners and Demolishers are the two classes that rarely get into the mission area and are very useful. Always select the best rated soldiers. Create a team where each class is represented, or one where all the classes are from the same planet to get a +5 team rating bonus. Do not spend all your coins on Bronze pack cards, because they are generally not worth it. Only use your bucks for the Gold Pack.