For equipment - You can carry up to what your troops can wear directly and have 0 crates. Once you have more items then troops you start to gain crates. Armor is on a 1-1 basis and weapons go by slots (each troops has 4 slots)
Your level of armed shown on the map (lightly armed, armed, heavily armed, shiny army) depends on how many sets of armor/weapons you have and the quality of those weapons. (Unfortunately it's not very reliable though and you can have 50 men and 1000 stones and be listed as like heavy armed, so seeing someone as armed doesn't give you that much info on what they have, you can be only armed if you have plate armor just not enough for all your troops, it is also possible to be listed as unarmed with equipment... so it's buggy)
EG. 100 men can carry 100 body armors, 100 hand armors, 100 leg armors, 100 head armors and a weapon for each man. This would show you as 0 crates, it would also so you as a level of armed.
If 100 men carried 200 body armors, 200 hand armors, 200 leg armors, 200 head armors and a load of weapons. This would show you as having crates, it would also so you as a level of armed.
Your best option is to buy some shitty gear enough to list you as armed then start trading with low levels goods (keep below around 200 crates). Start to save up some money and make some troops. If I was you I would build to around 500 troops then sell 400 of them.. do this a couple times whilst trading. (every place you visit look what gear they have available) Once you have some money start gearing a 500 man army. This is about the most viable trading size (before troop upkeep starts burn a whole in your pocket).