Ooh a chance to share some making tips. I would be happy to help. Firstly what sort of Budget are you looking at? Once you figure that out you can determine the best way to make your mask. The following methods are listed in order of cost and difficulty level.
The cheapest option would be making one out of cardboard. It is a super easy material to get and you would be surprised at how versatile it is and you can make it look pretty good. But it isn't the best for longevity.
Pepakura is a step up from using normal cardboard a very good way to make a mask out of cardboard. It takes a little longer but you have more control. You can also use fiberglass on the inside and bondo on the outside to make it very smooth much more resilient.
That is the best method I can think of for someone working on a tight budget. I recommend 200GSM cardboard and a quick dry pva glue.
Next stop in the craft making train is Yoga mats (aka EVA foam). Done in a Similar way to Pepakura, you print out a template on cardboard then cutting out the foam. Use a heat gun to shape the foam and quick dry cement to connect the pieces together.
Now I have experience with all before mentioned methods. But now we get to my area of expertise. 3d printing Using a 3d model and 3d printer in order to make the parts. This is the method I used to make Eljay's current mask and you can see a bit more about how I did that here.
Hope that helps, and If you have any more questions about each method feel free to ask.