To those struggling with Leaf, for the longer gaps between buildings, remember to dash off the ledge rather than jumping off. If you stand at the edge of the ledge and use the dash, you'll still be able to dash in midair after, unlike if you had jumped off. This lets you traverse a much further distance and reach the taller towers (as well as the floating islands outside of the race).
So: stand by the ledge, dash, jump while in the air, dash again, jump once more.