I think 2~3 of each iron is usually enough, that's how much I keep myself and I usually don't find myself needing tons of irons. yes silvers need them as cc fodder, but unless you're rushing awakening (which you shouldnt be, looking at your 250 max barracks), you won't need that many. in particular, you only really need to focus on soldier, archer, heavy and mage irons. the rest are very rarely needed. (and maybe bandit as a sub, but still not used all that often)