Since you say in the title this is your first build, a tip for you, which is a little late: You never want to start with the helmet. After you do a lot more of the suit, you'll have a much better grasp of how to do foam pepakura, and you'll be able to make a helmet which is much more accurately shaped. The first time I made an iron man suit I started with the helmet, got it wrong and too big, and then went back later and re-did it. 2nd attempt went much better.