If you are using base rules then armour is massively over-priced and you are better going for more troops over more armour. The only possible exception is your leader because they are irreplaceable, but even then most people just try to keep them supported and out of too much trouble.
In my circle people would tend to sell any armour they came across except gromril and just jump straight from no armour to gromril with shield (except the leader, he would get the best armour you found – noone would buy it though). We had to halve the cost of heavy and light armour and add +1 in melee to shields and bucklers before anyone would take it.
Oh yeah, that was the other thing. We had to nerf crits a bit so that not so many of them just punched through armour too. That also helped make armour useless.
Interestingly, changing toughened leathers from equipment to a class of light armour led to slightly less cheaping out on daggers for dual-wielding. 5 gold to give a henchman a 5+ save vs dagger wounds (and we all know how often you will wiff with 2 axe attacks and then wound with the dagger
) was pretty good for protecting mid-high value henchmen.
tldr: Way more cost-effective to ignore suits of armour entirely until you can get gromril and get only one melee (probably a club) and one ranged weapon per hero and one melee weapon (again, probably a club) per henchman and then equip later. Equip helmets as you find them, but don't bother buying them.
Take all of this with a grain of salt – it has been a long while since we played pure vanilla Mordheim.