Plenty of people sell adorable little kits (I've even written about a few), but when it comes down to it, you can really make your own quite easily.
Now, everyone has a different makeup routine, so feel free to add that fab red lipstick, or black liner that you can't live without. But here are some of the essentials I personally keep with me at all times:
They're a lifesaver. Honestly, having some deodorant wipes are perfect for if you happen to be going out after work, or if you just want to freshen up throughout the day. Using regular deodorant simply doesn't work after the first application. As I learned in high school from my health teacher, "putting deodorant on sweat doesn't do shit". I might be exaggerating a little, but you get the message. Also, pack makeup/facialcleansing wipes, which can keep your face smudge-free and underarms fresh and clean.
Clear nail polish
This stuff plays double duty in emergency situations--not only can it add shine to your nails, it can also patch up unfortunate nylon runs, act as a makeshift band-aid and even get rid of unsightly warts (yes, really). Don’t leave this one at home.
Something you don't really think about, but will be really happy that you have them. Preserve your fave earrings--and the awesomeness of your perfectly-accessorized outfit--by carrying some spare earring backs in case you lose one. It doesn't happen a lot, but trust me, you'll be grateful when you need one!
Any of you who has ever felt the horrifying pop as the button on your pants gives way knows that a safety pin or two is essential in preventing (or lessening the effect of) the dreaded wardrobe malfunction. It will hold things firmly in place, at least until you get home and can change into something else. They're good to have for multiple situations.
A small mirror
Sometimes makeup disasters strike without you even realizing. And that sucks. That’s why it’s absolutely crucial to keep a mirror with you at all times so that you can check on things--like that your lipstick is looking fab, your mascara hasn't caused a case of raccoon eyes and that you don't have any food in your teeth.
Keep all these things with you and you'll be good to go! Add in some lipgloss, or whatever else you might need throughout the day.