I have been a big costume for years. I'm not really into that sexy girl. So I made a Jellyfish Costume. I used a crabbing net I found at a yard sale. I cut a hole in the smaller part of the net and put the hula hoop in the middle to make it more round, and some old sheets bubble wrap a light up hula hoop puff paints, tape, glue, scissors, some tule and streamers and glow sticks for the tentacles. The light up hula hoop was awesome going out to the freakers ball and when people would bump into me the whole thing would light up. Also using the fishing net made it easy to just tie all the tenticles on to it.
It took me maybe 3 hours or so to make and cost about $30. It was a really fun costume to wear, I even had a bottle of hand sanatizer to squirt at people as jelly.