Troy Parker: Thanks I'm a noob lol! But should I make like two rounded pieces that are bigger than my head then sew it together and the cut it open and then put a zipper on the back? I'm gonna have some lenses inspired by tasm, If I can't do this I'm thinking about buying a red zentai mask and glue on the lenses.
Will sharpie work on spandex/lycra for the webbing?
Before you read this, know that I am NOT a professional at all...

you should wait and take tips from experienced makers before you do this, this is just if you can't wait to start. After some research, I thought this method would be easier after completely flopping at my first attempt at a mask.
Just cut the shirt so it's open, make sure you can wrap it around your head and there's no bare spots.
This^ is the way I'd go about a standalone mask.
This is what you're basically aiming for.
Think about it like a hood on a hoodie (but the cloth is shorter so it's tighter and hugs to your face, like a mask!)...
The dotted line going down the middle is say your forehead to your nose, you need to make the bottom half in a similar manner, add some excess for the part that'll connect to the top half, because you'll be stitching it (better to have excess cloth to cut off than not having enough and being stuck with a fairly uncomfortable mask). And remember, turn your mask/cloth pieces inside out and stitch them together, that way the flaps will be on the inside.
As for the neck zip... here's what you should be aiming for.
And yeah a Sharpie should work on those materials just fine.
If you've got a spare head

(ask somebody to help you out) you could make them wear the mask and then draw the lines, if you draw the lines when the mask isn't stretched out, the lines may look off/curved once stretched.
As for the eye holes, put the mask on and draw rough circles of where your eyes are (be careful) and then take your mask off and cut them out. But make sure that your eye holes aren't so big that you can see them poking out from underneath your lense. If you're using fairly large lenses, you've got no problem. Make the eye holes a little larger so your eyes are comfortable.
I'm sure there's experienced costume makers here laughing at this post, I'm just an amateur... well, worse.
Anyways, hope this helps you out a little if nothing.
EDIT: Oh and I'm sure I don't need to tell you this, but use thread that's the same colour as your mask so it's barely noticeable. Don't worry about the zipper/stich seams, you can run over them with the Sharpie when you're doing your web pattern so they're not noticeable.