Quality of a garment can come in two different ways, fabric or construction.
Fabric is easy to see the difference between luxury and performance, luxury cloth is softer and has more detail while performance cloth is usually made of basic patterns with a harder finish.
Construction of a garment is harder to detect with an untrained eye. Take jackets for example, they can be fused, half canvas or full canvas. Then you are looking for machine made versus handmade details.
Generally the more time and effort that it takes to construct the jacket the higher the quality. All have advantages and disadvantages, the question is do you want more pieces in your wardrobe or fewer pieces of higher quality.