The most fundamental part of any wardrobe are the staple items. Staple items can be used in almost any combination, and will generally make you look presentable without having to put too much thought into it. Owning at least one of each of these items will guarantee that you have something to wear for almost all occasions. Buying each of these items will probably take some time, but once you have them, they're incredibly versatile and should last you years if you take care of them. Replace them as necessary, and you have a foundational wardrobe for life.