I would add the neons first, wait a while then add the cories. I always felt it was best to add the bottom feeders at the end. This lets more 'stuff' build up on the substrate, giving the cories something to eat. I'm sure you would be fine if you added them right away but you would have to supplement their diet with some algae wafers or shrimp pellets. Also be sure your substrate is smooth, any sharp edges will damage the cories' barbels. Cories will become stressed and weak if they lose their barbels (mainly due to lack of food).