I have a simple method : I buy a thing only if I can answer most of these questions with a yes:

1. Do I genuinely need it and I can answer myself why I need it objectively?
2. Does it have a proper place where I can store it in my house ? If no, then don’t buy. Especially clothes.
3. Do I already have more of the same item? If yes, what novelty/advantage does this new item provide ? If nothing new, don’t buy.
4. Does it have utility ? If it’s just for attraction/decoration, I avoid buying it.
5. Can I buy it twice ? If yes, it gets more points in favour of buying.