I was looking to get crickets delivered, but got overwhelmed by the number of options. Do you have any advice for places that ship small numbers of crickets affordably?

Also, I have always struggled to keep crickets alive past a single week and a half. Pet store cricket food and gel water seems to make die off rates skyrocket. Fresh vegetables are better, but still not great. I wonder what I'm doing wrong. (Besides buying large crickets that may be near the end of their lives.)