First I found a pattern for a hooded sweatshirt, and a simple black tank top body suit and sewed them up, I literally drew where I wanted the black to fit while I was wearing it so they would land in the right place. I cut the back down the middle for a zipper and left a hole in the back of the hood from my head to get through! I also cut the hood fabric way bigger than the pattern asked then I used a large piece of paper to make the rest of the pattern pieces (the purple triangles on the arms, the back spider details etc) and made sure they fit my body perfectly by pining them to the suit while it was on. I did all the webbing by hand before sewing the pieces on using fabric paint from Walmart. It was definitely not an easy costume to make! I think the important thing is not to use too stretchy a fabric, as it will be hard to see it perfectly to your body shape. I hope that helps!! Let me know if you have more questions :)
Edit: Oops I meant to reply privately!!