Here are a few suggestions for racial oaths. I based most of these on some little snippet from their racial information on elanthipedia. Not sure if they should entirely be oaths to nature, so I went with a bit of variety. Feel free to use or adapt.
Dwarf: I will be steadfast.
Elf: I will align with the natural forces.
Elothean: I swear loyalty to nature.
Gnome: I will discern what is necessary.
Gor'Tog: I will protect and endure.
Halfling: I will find the right way.
Human: I will adapt and conquer.
Kaldar: I will honor the natural order.
Prydaen: I will be fearless and unwavering.
Rakash: For the earth, and for the Great Pack.
S'Kra Mur: I will strike hard and fast.
- Navesi