I started writing this right before the con ... then forgot that I hadn't actually posted it! Unfortunately I have only a few pictures for the second half. But hopefully it still makes sense.
After sewing the flames to the pants I hemmed the pants and sewed over the black border to secure the hem. I used black thread on top and yellow in the bobbin to hide these additional lines. I also sewed farther to the tip of the black to secure that part.
I had help pinning the hem since every time I moved the fabric shifted. (and for once I had help on-hand)
Then I had to think about the white section. First I thought of just making a second set of under-pants, but I thought it might shift and expose other things. Then I thought about sewing two sets of pants together (one white one the red/flame) but it might get bulky and hard to move. So instead I created pockets by taking what looked like a loin cloth, sewing in elastic, and attaching it to the opening of the red pants (and honestly create pockets whenever possible is always the answer).
Next I moved onto the earnings. I ended up making them twice. I found cheap earnings at Walmart for $3 but they had three loops. So I broke them apart and re glued the clasp to the smallest loop. I then used a foam sheet and cut out the shape for the earnings and used hot glue to form the shape and adhere them to the loop.
I then read that with parchment paper you could smooth out the hot glue. I then painted them silver with nail polish. Once done they were a bit bigger than I wanted so I re did them this time entirely with hot glue. I flattened and smoothed almost a stick of hot glue then cut a much smaller pattern out of that and just reheated sections to make it all stick together. I also cover it in silver nail polish.
The top was one of the easiest parts. I took stretch fabric and sewed it in a tube one way, then made a long thin tube of white fabric and sewed that into the seam to wrap around as if it was the entire top. Once I tried on the tube top I just adjusted the bottom to fit closer to my body and sewed the tube top slightly in on the bottom. I'll need a safety pin to pin the wrapped section to the tube top.
I invited a friend over to help with the wig. I decided Erza would really have a messy ponytail and was less careful about making it perfect, just tried to hide the wefts. I put on the wig and held it to my head while my friend pulled it into a ponytail.I then broke a mechanical pencil in half and used that as support in the base of the ponytail and wrapped it with green ribbon. I braided the ponytail to get it out of the way as I tried using wig gel and hairspray on the rest of the wig. Old hairspray doesn't work very well so I'll not be doing that again.
I was all set except that it's winter and she goes barefoot in this outfit so I bought toe socks and will wear flip-flops. When I got to the convention I realized a few things.
One: My feet slipped around in the socks
Two: I didn't bring all the makeup I needed, just foundation and
Three: That I left the temporary fairy tail tattoos at home ><
This prompted a quick trip to the CVS luckily only a few blocks away. I can't quite remember how much I spent, but it was at least $45 in makeup and poster board paper. I bought eyeliners stabilizing powder and spray and a variety of other makeup things recommended for "fake" tattoos. I traced the symbol onto the poster board, cut it out and then used my low temp hot glue to glue it to my arm so I could trace it with eye pencil. I let the hot glue cool down a bit before sticking it to my arm, I wouldn't recommend squeezing hot glue directly on your arm it would hurt. Once traced I filled it in with the eye pencil then traced it again with liquid eyeliner. I then sprayed it with the staying spray and dotted on the powder. I was so glad that the tattoo didn't smear during the day and I had quite a few people really in awe that I would actually get a real fairy tail tattoo! ^^ 
While I had extra poster board I also cut out feet. I put the cutouts on the bottom of my feet, then pulled the socks over them. I then added hot glue to the bottom of the socks. I was able to take the socks off while leaving the poster board inside for the glue to dry. This helped with traction for my "bare" feet. I had fun running around the convention and even ran into natsu! (happy was off somewhere else at the time ;)