Thin inside: In general, you want to wear lighter/thinner fabrics closer to your body, and heavier/thicker fabrics farther out. This rule is pretty obvious and usually happens naturally
3 layers max: When it comes to layering, three is sort of the magic number. Any more than that is usually overkill, and it can create a bulky, overstuffed look. example for a good layer jacket: https://extended-alpha.com/products/casual-jacket
Light inside: How do you combine different colors for a cool layered look? Wear lighter colors closer to your body, and wear darker colors farther from your body (outer layers).
Each layer work: Here's the final golden rule. You should always make sure each layer can be worn on its own. This means it needs to fit well and go with the rest of your outfit.