I'm not sure there is anything easier to dress as for Halloween than a calavera, or a skull from the day of the dead. You really only need some white make-up and a black make-up pencil. You can just use eyeliner if you have nothing else.
I braided my hair back, and put on my Frida Kahlo jewlery from last year, which I created for less than ten bucks from craft store jewelry piece. Wow, my hair grew like a weed this year. It is almost past my shoulders now. This year, I decided to combine my two favorite costumes--calavera and Frida Kahlo.
Beyond that, your imagination is your only confines. I like to look at other skull designs. You can design your face to have flowers, or hearts, or anything. You can use all kinds of colors. I chose to use only black and blue (around the eyes). I also decided to wear my felted flower crown.
And a full body shot. I am wearing a skirt my sister made for me last year. We went to JoAnn's and picked some random "Mexican-y" fabric. I love the way it turned out. I have to admit that I have never considered myself someone who would take pictures of herself, or speak in front of a camera for the whole interweb, but there is something so freeing in this costume. For me, at least.