You want at minimum a UV filter, which will always stay on the camera as it improves the colour of sky or makes no visible difference in other scenes, and it protects your expensive lens.
You most likely want a circular polarizer (dramatically reduce/eliminate reflections)
and if you are shooting in really bright backgrounds (snow, sand) you probably want a Neutral density filter (ND), probably a small assortment of them in varying degrees of transparancy.