I agree, just jump right in. The first thing I wanted to tackle was the helmet, since it is a symmetrical piece I knew that it would be tough. (I also wanted to do it first because, I didnt want to make armor parts then decide I didnt want to continue the suit and have nothing for display, but I ended up keeping at it) If you don't do it right and you make little mistakes, they can add up and make you helmet look off (i.e. the brim could look shifted to one side lol) I made a tester helmet for sizing, then made df4l's MKVI...then I decided to move up to FS HD MKVI. The first time I made the HD MKVI I messed it up a bit and it ended up being the way I described. So, I went back and made another one. After that I have done pretty well with everthing else I have made. The HD forearms had to be the hardest to me because of the size of the pieces and the size of the part. I would say if you have gotten as far as having the helmet and chest left then do the chest first, and then do the helmet. When you do the helmet, take your time and make sure when you put it together you check the symmetry of the part as your putting it together. Oh, and did I mention take your time, lol. Thats really all there is to it. Each piece is only as difficult as you make it seem really. Im sure others would say the chest is harder than the forearms, or the helmet is harder than the shins. Its all personal preference in my opinion. Hope this helps.
Also, when I was putting together the HD MKVI I did it in sections and went ahead and added the supports for each section so i knew they wouldnt be warped when I attached them all together (i.e. I made each side of the helmet in the chin area, then made the chin, then attached them together). Doing it that way helped me out alot, but if you do it this way, make sure you have the scaling right because you wont be able to try it on.