One of the first things that we are (hopefully) taught as children when it comes to money is the difference between a need and a want. Unfortunately, while it is very easy to point out a "want" to a child, that new toy or an ice cream, needs are a bit more difficult which leads to a bit of a grey area.
So I divide the idea of needs into primary and secondary needs.
Primary needs are what you need to live. Missing them tends to lead to a deterioration of health and then death. They are found on the bottom two tiers in Maslow's hierarchy of needs. You need water, food, air, shelter and access to appropriate medical care. Food does not mean caviar, it means basic nutrients that your body needs to survive. It doesn't even means variety in the food you eat, just that you can eat. Shelter doesn't mean owning a home. In certain cases a tent might suffice, or an apartment shared with a friend. Just something to protect you from the elements. Clothes would fit in here only as much as was needed to keep you healthy. You don't need a $1,000 coat, you need one that will keep you warm when it snows.
Secondary needs are what you need to get and keep a job that will provide the resources for your primary needs. This means appropriate clothing for your job (office ware for sales men, scrubs for nurses and steel toed boots for construction workers.) A cheap cell phone (pay as you go) so that you have contact info for your resume may be a need. Other misc. needs may include fees for a professional college or materials you are expected to provide yourselves. A car is only included if your job includes moving yourself and materials a considerable distance, such as a truck driver or a home health care nurse.
Everything else that you spend money on is a want. I doesn't make it bad, it just means you don't need it.