I use two tiers of whetstones
400grit: quite rough, good for blunt knives, gives them a new edge
1000grit: fine, makes the edge sharp, for general use it's really good, probably equivalent sharpness to buying a quality knife out of the box
and if you really care for your knives
6000grit: really fine, gives it a laser edge, good for cutting proteins (meat, fish, etc), with an edge this fine it'll get blunt quickly when cutting hard objects and may chip quite easily if cutting into bones, use this for a sashimi slicer like yanigiba or sujihiki, but not as a fillet knife unless you want to sharpen often
using whetstones you won't need sharpening steels or gadgets, just some water and the stones, but it takes time to learn. good luck! =D