Hello Kaahi! I'm in the same situation as you are: having a desire to build a mecha suit, but having no experience to back it all up. And wow...that Strike Noir image looks amazing. I want to make an RX-78-2 as you are, or an ARX-7 Arbalest from FMP, as they're relatively simple compared to some of the more-ridiculous (but still impressive) costumes. Yeah, like the Freedom Gundam that Goldy made. Very stunning.
Anyway, I looked up some methods to making them; the Vinyl Over Foam Tutorial
way seems much better and cleaner compared to the cardboard/foamboard/posterboard method; not very hard to get materials nor to put everything together. Able to be heat-shaped, it seems that curves can be easier to make as well, a definite plus if I want to build the Arbalest instead.
Now the problem for me is proportions. I'm 5'7", and my head's relatively large compared to my shoulders; I know that staying true to proportions is out of the question, but just how far should I go? Build platform soles, or omit them? Widen the shoulders? Put my head in the torso instead of the mecha's "head"? Hmm...
There's no rush for this, though. Hopefully, this can be finished by Setsucon 2008 in January (Penn State's awesome little convention), but Otakon 2008 seems reasonable as well.