You will need to get your hands on gold and Supply Tickets before you can get new clothes and skins. This can be achieved by completing an assortment of objectives each day, and by completing the game itself. When you have a decent amount of both go to the Store and locate the 'Supply' option.
Tap on 'Supply' to bring up two options to purchase one of two different crates. Each of these crates will contain at least one item and can be purchased using Gold or Supply Tickets. Remember that each time you purchase a crate using gold the cost of subsequent crates using this currency will increase.