You might want to go with NiMH rechargeable batteries. I have had issues with alkaline batteries leaking. If you choose alkaline only keep them in your camera when you are using it.
Typically a lens cap for a lens that takes a given size of filter will also work on most filters attached to the lens. There are exceptions like when you are using square filters.
One of the best classic portrait lenses is a fast 80-85mm on a full frame camera.i use a variety of lenses for architecture. For tall buildings a tilt-shift lens can be very helpful. A good rectilinear wide angle is also very useful.