The basic hierarchy
Amazon ads go campaign → ad group → keywords/targets. The campaign holds the budget; ad groups hold tightly-related products and their keywords. Keep ad groups focused so a single bid makes sense for everything inside.
A simple structure that works
One campaign per product (or close-knit group), split into an automatic campaign for discovery and a manual one for control. Within manual, group by match type so you can bid exact terms higher than broad. This makes performance and waste easy to spot.
Why structure protects margin
When campaigns overlap, they bid against each other and waste budget. A clean structure prevents that. AIAdKing reads your whole structure each night, flags campaigns competing for the same searches, and optimizes within it.