The extra charger suggested above is sound advice if you're getting extra batteries. That way you can continue to use the camera while the empty ones are recharging.
Other than that, with the 16/2.8 on the NEX-6, you're good for the time being; it's much more flexible than its single focal length suggests. The 16 is very, very sharp in the center, and allows a fair bit of cropping there. Use that experience to find out what your future lens needs are.
Oh, and there's one thing you really, really have to do, and that's to enable the quick-navi. Why it is off by default is a mystery to me; because once enabled, you can access all necessary shooting options without menu diving.