You hit it on the head, if you plan on running around in all purples, the best long term decision for your stable is to upgrade the armory. Personally I find it to be a bargain and an easy decision to make seeing as it works on all your gladiators forever. I'm only on level 5/6 and I rarely have gold problems.Last month, as I was already struggling to repair my purple gears and heal my wounds, I made the decision to invest in Armoury level 6 instead of buying better purple armor gears for my warriors and I don't regret it as I make more money now than before the update, enough to pay all repairs and healing (and achievements ) and even have money left to buy a few green armor gears that are better than my outdated purple ones !
In fact, it's probably the best long-term strategic decision I made for my stable and I recommend everyone who can afford to do so if this money problem is not solved..