Cories are not a good choice to put into an uncycled tank. You will likely lose some, if not all of them. Trust me..even though I had readings indicating my tank was fully cycled...once I tried to build up a school of them, thinking I was being cautious--the bioload crashed the cycle. A new tank can be a delicate environment. Go slow. Go very slow. If I could do it all over again, I would have started with just the hardier zebra danios and added the cories much, much later, and in groups of no more than 2 at a time. Cories are gentle, sweet fish who seem to help each other out when one gets sick. It is a sad horrible feeling to watch one get sick and die due to a new tank struggling to stabilize. Best of luck to you.
p.s. about feeding cories, they will eat just about anything that comes to the bottom or even stuff that floats on the top. But they enjoy foods in wafer form. And if you are using a 1-3mm sand substrate, Hikari Micro-pellets are fun for them to find. They sift through the sand for the pellets. Freeze dried bloodworms and tubifex are also a good treat. I would advise to sticking to foods that say specifically on the package that they've been processed to avoid viral and/or bacterial contamination. That would be most of the Hikari line, I think. This is at least while you're starting out. It's just one less potential source of illness to worry about when the tank and fish are new.