[Alneyan]

You can rely on other commanders (for example, summoned flyers like the Harbinger) to get to that level of speed, or use the Gift of Reason spell (Thaumaturgy 4). This ritual will make a chosen unit a commander, enabling your Knight to traval at full speed on his own.

Gift of Reason is also a nature spell, something Man is good at, so it should be considered. Gift of Reason will also give your unit equipment slots, allowing you to strengthen it with various magic items.