At the very minumum, if you wear makeup, you should have these basic items in your set. They don't have to be these exact brands, or even built into a palette (although it makes things much easier), the idea is that you have them accessible to you for those days where you don't want to even have to think about what makeup to put on. It's your basic neutral color combo that can work in any situation. This is the shadow I am wearing in 90% of my outfit posts.
1. An all over base shadow. This is a color that most closely resembles your natural skin tone, and will blend well into your other neutrals seamlessly. (MAC Brule shown here).
2. A highlighter shadow. This goes on your brow bone and near your tear ducts if you want to get fancy (MAC Vanilla shown here).
3. A crease color. This shade should be much warmer than your base color, you have lots of options here so just find something that suits your taste (I am pretty sure I have MAC Cork shown here, but I can't figure out how to pop my shadows back out of the palette to confirm, sorry!).
4. A Brow filler/eyeliner. This is a color that you can use to fill in your brows (if you need it) or to line your eye (MAC Mystery shown here which is a great color for fair brunettes with light eyes). This color can also be used as a crease color when you want to get more dramatic.
1. An all over shadow brush for applying your base/highlighter (Real Techniques shadow brush shown here which came in a travel essentials set).
2. A blending brush to work in your crease color (MAC 217).
3. A fine liner brush for filling in brows and lining your eyes (MAC 266).