The track so far is all Fleischmann — not necessarily the cheapest, but it looks quite good with the ballasted base, and it’s widely available. The curves and station pointwork are in fixed geometry track, while most of the straight sections use flexi-track to reduce the number of rail joints.
As the layout was designed from the start for computer control, I put in a lot of insulated rail joiners to provide isolated sections for current detection.
Having pinned down the track, I found that a problem with the Fleischmann track elements is that the points have a slightly thicker base than the standard track elements. When you attach it to a hard surface, like my pine tabletops, these “steps” in the track base lead to uneven running, and need quite a bit of fiddling with thin cardboard spacers to sort out.
For ballast between the tracks, I’ve used Noch ballasted paper as a quick fix for the straight sections, and for the curves and fiddly bits granite chippings with the traditional dilute glue solution and pipette technique.