PVE
highs - heavy missiles launchers.....duh

If you have the fitting skills throw in a salvager or a drone link augmentor
mids - 2 large shield extenders, 4x passive shield resistance amplifiers (specific for each mission - ie 2x em 2x thermal for sansha missions)
lows - full shield power relays for maximum tank. Swap out relays for ballistic controls to maximize killing speed.
PVP
here you have alot more variation, since some people prefer to use heavy assault missiles, some people prefer to use microwarpdrive, etc. The standard fit involves missiles of some kind, 2-3 ballistic controls, 2 large shield extenders, and 1-2 invulnerability fields.
substitute named/t2 items as needed of course.