Assuming you are going to be shooting standard targets.......
The foresight element should be of the ring type, the size of which is dependent on the target you are shooting. Ideally you should see a thin white border around the target when the foresight is aimed. The size of the white border is down to personal preference but should allow you to judge that it is equal thickness all the way around the target. The rear sight will usually have an adjustable iris either by use of a rotating disk with preset apertures or a camera iris type which are fully adjustable. Again this comes down to personal preference and ambient light conditions, you don't want to small an aperture or the image will be too dark, to large an aperture and you may have eye alignment problems. Then there are coloured lenses that you add for contrast.
I'm telling you it moved!