Warmark
Sentinel
Ah but then you wont know who some of the npc's are since they appear in all games. Especially the shadow master who was the main hero in two of the expansions. I loved his story and his fight against destiny.
It wont hurt a new player to play the first three since it only cost $5-10 for the platinum version. I consider it money well spent since you get over 100 hrs of enjoyment.
That's something modern games cant give you.
Even though Spellforce 2 has never really been off my computer I only ever played Spellforce 1 briefly way back when and never any of the expansions for it, maybe it's time to pick up the platinum version from GOG and go prequel with it.