I had a left over bag of Timothy hay from when I had hamsters. I am using that as bedding for the crickets and it has made a HUGE difference to the smell. Like it's hard to believe how much better the tank is with that as bedding. The stuff is pretty cheap especially if you get the big bag.
I've been feeding mine cooking scraps and they seem to devour everything. Carrot peels, potato peels, tomato cores, lettuce leaves, apple peels and so on. I also crush (just a bit) some cat food and throw that in there as a protein source. When I grab some dandelion leaves from the yard for my beardie, I grab a bunch for them too. Strawberry tops and blueberries that are no longer firm (I'm picky) also get tossed in there.
I use a yogurt container lid to put some water crystals on so that it's easy to pull that out and rinse.
Basically, your crickets can and will eat almost anything. That's their role in nature. They eat stuff. Like all the stuff.