If you don't use makeup often be sure to practice it beforehand, especially with eyeliner. If not you might be stuck applying and reapplying it until it looks right, and it takes up much time.
Ah! And my basic bag has: One creme concealer, one crayon concealer, primer, nude eye shadow pallet, mascara, liquid liner, foundation/bb creme, blush, crayon liner, lash glue, lashes, lip color.
But every person's bag varies on what they use and who they cosplay, its best to take your time with trying out different applications to decide what you want to get.