Oats didn't work well when I once tried them. Wheat bran flakes (not to be confused with breakfast cereal) works best for me.
As far as fruits/vegetables, many things will work. You can be creative... Last couple years I've successfully used zucchini (those whales that get hugh before you find them), and watermelon rinds, to name a couple. A key point with the fruits/veggies is to give thin slices that can be eaten in a day or so so they don't have a chance to mold. And don't add fruit/veggie too often -- once or twice a week, depending on season/heat/dryness -- so substrate doesn't get moldy.
As far as fruits/vegetables, many things will work. You can be creative... Last couple years I've successfully used zucchini (those whales that get hugh before you find them), and watermelon rinds, to name a couple. A key point with the fruits/veggies is to give thin slices that can be eaten in a day or so so they don't have a chance to mold. And don't add fruit/veggie too often -- once or twice a week, depending on season/heat/dryness -- so substrate doesn't get moldy.