My husband has owned 100s of stick insects. He says they can’t eat all leaves and says the best way to select a plant is the plant it is on. Failing that fresh eucalyptus or privot hedge are the most versatile if you don’t know what type of stick insect you have. Make some cuttings, keep them in a jar of water to keep them fresh and replace every few days.

My daughter’s kinder class had their own pet insect bugs. They’ve always just kept them in with fresh leaves and topped them up as needed, removed one ones. They seemed to do well like this in this kind of enclosure. Hope it helps!

Pretty sure they eat leaved and plants etc not meats or grains

Aren’t they herbivores? I’m sure they eat plants. I’d be googling for some ideas