dont forget other than the obvious make up items - hand santiser, white towel to place your kit on if your doing make up at someones house, disposable mascara wands, lipbrushes or gloss wands, sponges if you use them, a palette or tile to mix foundations or concealors on, spatula, brush cleaner (spray) to clean brushes between people, a face chart if its a trial, a camera, tissues, q tips, moisturiser or primer what ever u think is best, perhaps some empty lipgloss containers incase you mix a gloss or lippie with pigments for a special occasion if you dont have an exact colour..
i think they are the other less obvious essentials