Sorry for the lack of replies.

I feed my crickets oats, spinach, lettuce, and carrots, though I've heard that feeding them a big variety of vegetables such as squash, slices of apple, banana, and other vegetables works fine.
The water gel is effective. If the gel seems to have gone dry, mist it with a water sprayer filled with dechlorinated water.

The egg crates help the crickets feel safer, and give them hiding spots. Also, it is easier to catch them from the cardboard egg crates than in the open.