I am an expert at getting free clothing. For some reason when people see me they like to give me clothes. (Maybe because I look like a small child or seem to be perpetually cold?) Either way, a lot of my clothing comes from someone else. My favorite shirt at the moment I stole (with permission) from the free clothes bin at my summer internship when they were moving and had to downsize. As some who loves free and cheap clothing I hate to say it but sometimes you have to shell out the money for quality clothing but what are the most important things to buy for your wardrobe?
Buy a least one or two good pairs of blue jeans, in your preferred style, but I would advise sticking to something that won't go out of style. I've had the same few pairs of jeans since I was in 9th grade (it helps that I haven't really grown since then but that is besides the point.) A good pair of jeans can last a long time and also are a necessity in any wardrobe and can be paired with almost anything.
Now our definitions of class may not match but it should at least cover what needs to be covered. This is a dress that can sit in your closet until it is needed but trust me you will need it eventually. Usually black is a good color because you can use it for things like interviews or anytime you need to look like a "proper adult." Also, never underestimate the power of a good sheath dress. If you are going for the suit make sure it fits well. Nothing is worse looking than an ill-fitting suit.
I'm going to be biased for a moment and tell you to invest in a good pair of Dr. Martens. They last forever and never go out of style. I wear my Dr. Martens every day and I've had them for over a year without much wear. They are also the type of shoe that looks good with a bit of wear and tear on them. (You may also need to buy a fancier shoe to go with that dress or suit as well).
4. Cardigan or Blazer
These are the best way to transform a top from casual to professional. They are also good for those days where you have to wear a certain top (that may not protect you from the elements) and need that extra layer to stay warm. Blazers are usually better in fancier situations while cardigans are good for everyday use.
Now don't spend money just based on the brand name. Buy a bag based on quality. If it is a purse or bag that you are going to be using for a long time or are going to be using to cart around those heavy college textbooks you are going to want something that lasts. Spend the money on the quality products. I enjoy canvas bags because the material is tough, so you can use it longer.