Most land turtles are herbivores, which means they mainly eat plants. While some land turtles have been seen eating insects, it usually isn't on purpose, and typically the insect just got in the way of what the turtle was eating.
Most herbivore turtles prefer eating leafy greens and vegetables. Some enjoy fruit and even flowers. Ideally, consider a turtle's natural habitat when considering what to feed the animal. Things it finds in nature are typically healthier for the turtle. It's important to avoid feeding land turtles dairy products. In general, turtles can't digest the lactose in milk products, which makes them sick.