The U.S. Department of Energy says, 78 degrees is the most cost-effective AC setting. I do that and turn on the celling fan on low and it seems to work great.
In terms of a nighttime temp, they say that is a personal choice, but it’s cooler than the daytime temp. For me, it’s 5 degrees cooler than the daytime, so 72.
What about when you’re not home? That should be 5 degrees above the temp you have when you’re home.
Check out all the info here: What Temperature Should You Set Your Air Conditioner in the Summer?