The path alongside the Foss from the Brigadier Gerard roundabout, heading North to Haxby is really nice but best saved for when the ground is hard. You could turn it into a loop by coming off at All Saints’ church in Earswick, cutting across to the path along the West side of the railway and then through Clifton to the YHA and alongside the Ouse back into town.
The paths around Fulford golf course are really nice and mostly good underfoot. The bit between Heslington Common, where the groundskeepers have desperately tried to make it look Scottish with transplanted heather and gorse, and Tillmire SSSI is really nice in spring because it attracts lots of wildlife.