This is the simplest way to do the bun. it looks decent and is super cheap!
-very small piece of cloth.
1. Get a piece of cloth (in whatever color you need) and cut it into a cirle to hold your hair/wig.
2. Get a pair of scissors and cut holes around the ends of the cloth. they should be about 1/2 inch apart. it dosent really matter. xD
3. get a hair tie. cut the hair tie in half so it's just one string. (cut off the metal part if it has one.) the hair tie should be new so it wonn't stretch out.
4. go over-under with the hair tie into the holes.
5. when they meet, get your glue gun and glue it together. hold them together and let it dry.
6. (this is optional) for extra support, i used a small rectangular piece of cloth and glued around the glued ends of the hair tie. wait for it to dry and voila! youre done.
for decorative touches you can used the string and after everything, you can over-under it into the holes where the hair tie is.
i will post pictures after AX. xD
hope this helps!