Basically, let your interests decide what you invest in. If you buy the gear and just try to use it, you might find you don't really have the enthusiasm to.
Look at other's work as much as possible, if you like a shot make a note of it, you might find you like a lot of a certain type of shots. Try to emulate them first and look into the equipment that allows you to do this. You will eventually evolve your own style.
As everyone has already said, pick up at least one spare battery, to allow you to keep shooting, and then kit to allow you to look after what you already have e.g. cleaning kit, camera bag, UV filters for your lenses.