Since he is so basic, genderbending him is going to be very hard in two aspects.... one being to find things to genderbend, and two being, if you genderbend someone with unnoticeable traits, you will hardly be recognized.
Do you have anything you plan to wear that will stand out and say "PETER PARKER!" or "SPIDERMAN!"?.... I mean, seeing someone cosplaying him is already, maybe just to me, I dunno, would look like a typical nerdy person, however, turning the look female would make it even more unidentifiable to me. x:....
Since we ARE going nerdy though, how about a pleaded skirt?.... make it like you are a school girl, all private-schooly, you know?... Obviously, then you have makeup. From there, I really don't know. Maybe spider decal fingernails. x:
Cosplay 1: Sailor Venus (Commissioner failed to make 4 month deadline)
Update: August 10th.... still nothing.
Reality: Recycled or no cosplay at all. Got to love commissioning! Thanks everyone!! Serious thanks to Dulcinea, who actually made the deadline for the accessories far in advance and of outstanding quality. Sucks they won't be used.