Here is my progress so far using gimpee's pepakura file. Had a few issues with pieces not fitting right like the cheeks so I will have to look into that before finishing. For the most part the build is going well.
Update 4/2/15- A few progress pics. Plastidip skills suck and made my helm worse. LOL I think it was too thick since it was a cooler day outside so it didnt spread as thinly as normal. Hopefully its fixable. The boots have so many tiny parts to cut out, should have looked around for that simplified version before starting.
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.
This one at least fit surprisingly well and I already planned of getting a resin helmet to make it easier to wire and have opening faceplate. Was trying to get the foam one done in time for the premiere. It made for a good learning tool for building, sealing, and painting.
I always say to start with the helmet. If you can't get that to fit right then the rest will be worst. Best thing to do for sizing is to start by figuring out the total hight of the pep suit that your making and make it a half an inch or so taller that your own hight. Then go into pepakura and use the measure from point to point tool and compare all the dimensions of the separate parts to your own dimensions. And adjust scale from there.