Increase the control sensitivity in the settings menu. It will give you more aiming control and let you use your reflexes more effectively. Since the in-game credits are not so easy to come by, don't squander them on cosmetic improvements. Instead, use them to improve stats like accuracy. Keep in mind that snipers can hit you even when you're in a cover. Use the snipers' red beam to locate them quickly and eliminate them before all other enemies. Reloading automatically gets your character back into cover, so use it to your advantage. You could reload as soon as you hit a couple of enemies, just in case. Since you only get a limited amount of grenades at the start of the game, wait for some tough situations to use them. They cost a lot and generally aren't worth spending your money. The best time to shoot a drone is when it's hovering over some enemies. The small explosion that happens can provide some additional damage.