The spinach is probably wilted because it has just been planted. Keep the water up to it in the morning and night and it will come good. Everytime you replant a plant, you disturb its root system and stress it out so it needs time to recover.
As for keeping away pests. You can go the chemical insecticides. More natural options are pyrethrum which comes from a plant. My mum also used to mix chilli, garlic and slightly soapy water together in a spray bottle and used that to spray on the plants to keep the bugs at bay. It also depends on what is eating your plants.Putting fine netting over the top might keep larger bugs like grasshoppers at bay.