What is the best home made bug killer for indoor and outdoor plants?

Really depends on what plants and insects?

https://www.treehugger.com/lawn-garden/8-natural-homemade-insecticides-save-your-garden-without-killing-earth.html

lemon

Water in a squirt bottle with a few drops of Dawn.

Hey neighbor! I'm in the Upstate as well. This is the bug capitol of the world, although we don't get any accolades for it;) I use castile soap diluted one teaspoon to a quart for things like mealybugs and aphids. For fungus gnats, sprinkle the soil with cinnamon. Outside I use kaolin clay to protect my plants from chewers and suckers. Diatomaceous Earth for ants. I also have several bird feeders, the birds help to control several types of bugs. It is a never ending battle with all kinds of creepy crawlers in this neck of the woods.

Diatomaceous earth (DE) is not only inexpensive and effective; it's non-toxic to kids, birds, and pets. And yet it destroys ants, earwigs, slugs, beetles, ticks, fleas, cockroaches, and bed bugs. As these pasts move across the powder, it sticks to their feet and legs only to get into their joints and exoskeleton.

Thanks neighbor, I will give your recommendations a try!