A mix of spells with a reasonable amount of combat potential. It's all up for discussion, though.
0 - create water, cure minor wounds, detect poison, guidance, purify food and drink, resistance
1 - calm animals, entangle, faerie fire, longstrider, produce flame, speak with animals
2 - animal messenger, barkskin, flameblade, summon nature's ally II, tree shape
3 - cure moderate wounds, daylight, plant growth, sleet storm, spike growth
4 - air walk, command plants, freedom of movement, rusting grasp
5 - commune with nature, insect plague, wall of thorns
6 - greater dispel magic, summon nature's ally VI