Hi there and welcome to this forum! I think it's great that you wanna go out for an adventure like this .
I recommend that you get in contact with your local garrison and look at their armor to get a glimpse of the sizes and shapes of the different pieces.
When it comes to shapes and sizes, there is a clear difference between screen-accurate (TE-derived) armor, and the FX armor. The FX armor kit is in general larger than the screen-accurate armor, it is made this way so it can be trimmed and assembled to fit a range of body types. The screen accurate armor on the other side, was sculpted on a mannequin (from an average body). I don't know if they sculpted the FX on top of a mannequin, but I think sculpting the armor on a mannequin would definately be a great advantage. This way, it is much easier to get the proportions right. But of course, having a big sculpt also has its own problems in terms of storage and logistic (My mom is a sculptor so I've experienced that before )
Have you thought about what kind of clay you want to use?