I have used fruit before (when no veggies could be found) and they were things like apple and pear. You want to avoid something with a lot of moisture (nothing like mango or something that literally drips juice) because this will spoil the oatmeal and you'll have to throw it out.

Veggies just provide moisture. I have used broccoli stem too, but many people like to use carrot or potato.

It is a waiting game though. It took me months to get even two containers of itty bitty mealworms. Of course I started off with only a few mealworms (around 100-150). That was also in a cooler environment (70 degrees). The room I have them in now is at the very least 75 degrees, but can reach 80 during a hot day. I get about 3-5 pupa a day at this temperature range.