Try to complete the Special Challenge and Daily Orders whenver possible as doing so will earn you Company Coin which can be used to unlock weapon and vehicle progression options. They also allow you to purchase cosmetic items such as face paint, jackets, and weapon skins. Special Assignments are a series of in-game tasks that Challenge your sills on the battlefield while Daily Orders tend to be smaller challenges that rotate daily. These can be things like destroying a set number of enemy vehicles or resuppling teammates a certain number of times.