I asked the same question on this forum over a decade ago and I would recommend both Kohan I and II. There are enough differences between them you can appreciate both. Also I believe Kohan I’s sprite graphics are still pretty charming. Although the campaigns are…well, they are what they are. Skirmish my dude.
P.S. Ahriman’s Gift is a standalone expansion/campaign to Kohan 1 AKA Immortal Sovereigns.