Making a set of mjolnir armour is not easy or cheap.
You can either buy one privately from the members here (not exactly pocket money) or make your own using templates or ideas on this forum(Not cheap in materials or time)
Either way the answer to your question can't be answer in a single reply. You might try reading some of the threads..?
well if your fiberglass armor is thick enough, and weel made it wont need much other than cleaning.
But if your serious about making it out of metal, go with .063 - .080" thick aluminum, but your talking about alot of man hours, welding, you name it! It can be done, its just alot of work. Dont use steel, or even stainless, its a hell of alot harder to deal with, and it rusts, not to mention its heavy even in the .020 - .032" thicknesses.
(Quote from star wars (Good Luck,....your gonna need it!))