Learn to tell the quality of clothes so you can spot an actual bargain and not be duped into overspending on a label. There are lots of you tube videos that will show you what to look for.
Squeeze the fabric in your hand for about 30 seconds to see how it will wrinkle with body heat. And look at your hand through the fabric.
Look at the seams to see if the weave of the fabric lines up- if it doesn’t it won’t wash well. Even better if the pattern lines up as well.
Look inside the back collar and along the shoulder seams. These need to be reinforced or they will sag quite quickly.
Some cuts are more classic than others - shirts/blouses with a yoke will last longer than those without which are fine for fast fashion but won’t last as long. Never buy an unlined coat or jacket.
Avoid white, cream and light beige unless you can actually afford the cleaning bills.